Mechanism for securing then deploying a rotationally coupled rigid member to and from a frame via retention then release of tension in a curved member

A mechanism secures and then deploys a rotationally coupled rigid member to and from a frame. One end of a curved member is pinned to the rigid member and the other end is on or in a reaction guiding element. In a closed state, the curved member is straightened from its originally manufactured or “free state” curvature and the other end is secured to the frame via a latch mechanism. The tension in the straightened curved member serves to preload the rigid member against the frame. To move to an open state, the latch mechanism is released allowing the other end of the curved member to move with or within the reaction guiding element along a constrained path towards its free state curvature. The curved member reacts against the frame, the pinned end in the rigid member and the reaction guiding element to rotate the rigid member away from the frame.

BACKGROUND

Field

This disclosure relates to mechanisms for securing and deploying rotationally coupled rigid members (e.g., covers or aerodynamic surfaces) to and from a frame (e.g., airframes such as missiles, guided projectiles, unmanned aerial vehicles (UAVs), Small Diameter Bombs (SDBs), Miniature Air-Launched Decoys (MALDs) and the like, land/sea/space-based platforms or commercial products).

Description of the Related Art

Mechanisms can be used to secure a rigid member to a frame in a “closed” position or to deploy a rigid member from the frame to an “open” position. In one class, the rigid member is rotationally coupled to a frame at a pivot point. The mechanism preferably preloads the rigid member to secure it against the frame in the closed position. To deploy the rigid member to the open position, the mechanism releases the preload and applies a moment about the pivot point to rotate the rigid member away from the frame.

Airframes such as missiles, guided projectiles, unmanned aerial vehicles (UAVs), Small Diameter Bombs (SDBs), Miniature Air-Launched Decoys (MALDs) and the like need to secure “covers” such as shrouds, fairings, hatches or the like and “aerodynamic surfaces” such as wings, fins, canards or the like both pre-flight and during flight and to deploy the covers or aerodynamic surfaces in flight. In certain systems, the aerodynamic surfaces are stowed in or against the airframe and deployed at launch or in flight. It is critical that such covers or aerodynamic surfaces do not open prematurely (e.g., due to inflight airframe flex) and open quickly and reliably when commanded during flight. In many airframes, the volume available to accommodate the mechanism to secure and deploy the covers or aerodynamic surfaces is limited. A mechanism is positioned within the airframe to secure the surface and then drive the surface into the open position. The mechanism may typically include motor driven gear assemblies, springs, pyrotechnic charges or pistons. See U.S. Pat. Nos. 11,274,907; 8,540,809; 10,429,159 and U.S. Pub. No 2017/0336148.

SUMMARY

The following is a summary that provides a basic understanding of some aspects of the disclosure. This summary is not intended to identify key or critical elements of the disclosure or to delineate the scope of the disclosure. Its sole purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description and the defining claims that are presented later.

The present disclosure provides a mechanism that secures and then deploys a rotationally coupled rigid member to and from a frame such as a cover or aerodynamic surface on an airframe (e.g., missiles, guided projectiles, unmanned aerial vehicles (UAVs), Small Diameter Bombs (SDBs), Miniature Air-Launched Decoys (MALDs) and the like.) One end of a curved member is pinned to the rigid member and the other end of the curved member is on or in a reaction guiding element. In a closed state, the curved member is straightened from its originally manufactured or “free state” curvature and the other end is secured to the frame via a latch mechanism. The tension in the straightened member serves to preload the rigid member against the frame. To move to an open state, the latch mechanism is released allowing the other end of the curved member to move with or within the reaction guiding element along a constrained path towards its free state curvature. The curved member reacts against the frame, the pinned end in the rigid member and the reaction guiding element to produce a moment that rotates the rigid member away from the frame.

In different embodiments, the reaction guiding element may include a slot, a reaction plate or a linkage that both constrain the movement of the released end of the curved member along a path and provide a surface against which the released end reacts to rotate the rigid member away from the frame.

In different embodiments, the latch mechanism can be a one-time mechanism such as a bolt cutter, explosive bolt, frangible bolt, explosive nut, separation nut or pulled pin or a repetitive mechanism such as a manually actuated latch.

In different embodiments, in the closed state the curved member may or may not contact the frame. If the curved member does not contact the frame there is no reaction producing a moment that would lessen the preloading of the rigid member to the frame. If the curved member does contact the frame a reduction in preload will occur but may be outweighed by either the impact shock reducing benefits of such contact upon release of the curved member or a reduced lag in opening the rigid member.

In different embodiments, the curved member is formed from a material such as metal or plastic that can be straightened to store energy in tension without exceeding the material's elastic limit so that when released, the curved member will return to its originally manufactured or free state curvature. High tensile strength components with lower elastic moduli are generally preferred to maximize stored energy when straightened.

In an embodiment, a plurality of curved members can be used in parallel in one mechanism. A plurality of these springs will appear much like a leaf spring stack, but the loads on them will be different to maximize stored energy and deflection. A typical leaf spring may work in this invention but is expected to be suboptimal.

These and other features and advantages of the disclosure will be apparent to those skilled in the art from the following detailed description of preferred embodiments, taken together with the accompanying drawings, in which:

DETAILED DESCRIPTION

A mechanism secures and then deploys a rotationally coupled rigid member to and from a frame. The mechanism includes a curved member that is “straightened” to produce tension in the member that acts to preload the rigid member against the frame. When the tension is released, the curved member returns towards its original manufactured or “free state” curvature thereby reacting with the frame to rotate the rigid member away from the frame.

The mechanism is generally useful for any application in which a rotationally coupled rigid member needs to be preloaded to secure it against a frame and then forced open to rotate it away from the frame. The rigid member may be a cover such as a shroud, fairing, door or the like or an aerodynamic surface such as a wing, canard, fin or the like. The frame can be an airframe (e.g., missiles, guided projectiles, unmanned aerial vehicles (UAVs), Small Diameter Bombs (SDBs), Miniature Air-Launched Decoys (MALDs) and the like), land/sea/space-based platforms or commercial products. The mechanism may be configured for one-time or repetitive use.

The mechanism is compact and can fit in a constrained space. The mechanism can be easily modified to accommodate changes in either the frame or rigid member geometry. The mechanism generates minimal debris in operation, is easy to manufacture and is highly reliable, having few components and points of failure.

Referring now toFIGS.1A-1D, a rigid member100is configured to rotate about a pivot point102on a frame104. A mechanism106is configured to both preload the rigid member100to hold it against frame104in a closed state and, when commanded, to release the preload and apply a reaction force to rotate the rigid member100about pivot point102to an open state.

In an embodiment, mechanism106includes a curved member108that has a non-zero curvature in its originally manufactured or free-state (no stored energy), a reaction guiding element110and a latch mechanism112. Curved member108has a first end114that is pinned to rigid member100at a point offset from pivot point102and a second end116on or in reaction guiding element110.

Latch mechanism112is configured to initially secure the second end116of the curved member108on or in the reaction guiding element110and to the frame104. This creates a load105at a position offset from the pivot point102to put the curved member108under tension thereby straightening the curved member108to produce a first moment118in a rotational direction that preloads the rigid member100against the frame104in the closed-state. The frame produces a reactive force111into rigid member100and pivot point102produces a pivot reaction113. Note, “straightening” the curved member108does not mean that the curved member108becomes straight, merely that it is put under tension to reduce the curvature of curved member108. As shown, in this embodiment in the closed-state, the curved member108does not contact frame104, instead there is a gap between the curved member108and the frame104. Alternately, curved member108could touch the frame104having the possible beneficial effects of reducing deployment shock or reducing lag time when released.

Latch mechanism112is configured to, when commanded, release the second end116of the curved member108to allow the second end116to move with or within the reaction guiding element110, along a constrained path, to release tension in the curved member108and return the curved member108towards its non-zero curvature in the free state. The curved member108reacts with the frame104at a position119offset from the pivot point102where the curved member108contacts the frame104producing a frame force115on the curved member108, reacts with the rigid member100at pinned first end114producing a reaction load117, and reacts with a surface of the reaction guiding element110at the free second end116of the curved member108producing a reaction load121to produce a second moment120in a second rotational direction opposite the first rotational direction to rotate the rigid member100about the pivot point102away from the frame104. Curved member108must contact frame104prior to reaching its free-state such that the curved member108retains energy to react with the frame104.

In the closed-state, the force105of the latch mechanism112pulling the curved member108in one direction, combined with spacing of the pivot point102and its reaction force113away from the latching force vector105causes a couple to form between the two vectors, resulting in the moment118that causes the rigid member100via the curved member108to be pulled against the frame104and the frame104to have a reactionary force vector111against the rigid member100resulting in the rigid member100being preloaded into the closed position.

To release the rigid member100to the open-state, the latch mechanism112releases the second end116of the curved member108allowing the curved member108to return towards its free-state, such that the force vector115of the frame104reacting against the curved member108, combined with the spacing of the point of contact119away from the pivot point102and its reaction force113, results in the moment120that is created between the two vectors causing the rigid member100to rotate about pivot point102and open with respect to frame104. As the curvature of the curved member108increases towards its free state curvature, the rigid member100will continue to open.

Reaction guiding element110is a feature that provides a constrained path for the second end116of the curved member108to move on or in once it is released from the latching mechanism112. As the rigid member100is being moved away from the frame104, the reaction guiding element110provides a surface(s) for the curved member108to react against. When in combination with the curved member108reacting against the rigid member100at the first end114, and the frame104; the reaction guiding element110provides for another area for the curved member108to react against to move the rigid member100away from the frame104. It is understood that the reaction guiding element110can be attached to the rigid member100or to the frame104. As the stored energy is released from the curved member108, the freed end116will move rapidly as the curved member108returns towards its free-state. Controlling the bouncing of the freed end116and managing friction along the constrained path will be important considerations in the design. As will be illustrated below, the slot feature allows the greatest tunability by trading a straight slot with various curved options. A reaction plate that moves the curved member away from the frame will simplify the fabrication of the system, but will have a less predictable rebound of the free end of the curved member in operation.

The curved member108will have design considerations that are common with spring elements. Spring elements are a way to store energy to perform work in systems; therefore maximizing energy stored is often a major consideration for the design. As such, two key parameters to maximize energy stored in the curved member will be its geometry and its material.

Geometry will be driven to a degree by fabrication approach. It will be manufactured in the curved shape which will be its “free state”. Fabrication could involve forming from a bar and bending it into this shape or by machining a carefully selected profile from a plate of material. By choosing machining, the curved member thickness and profile can be tuned to maximize the energy stored within the spring while avoiding yielding or taking a set.

Choosing a material for the curved member is critical to maximize energy stored in the component. A material with a high elastic limit (strength) with lower elastic moduli (stiffness) is preferred to maximize the stored energy. Elastic limit is defined as “the greatest stress that an elastic solid can sustain without undergoing permanent deformation”. For airframe components weight is a driving design constraint. Steel and titanium alloys are common choices because the ratio of strength to stiffness is good. Composite materials such as an epoxy resin system with a carbon fiber reinforcement would also work well because the layup can be tuned to increase strength and allow flexing. The weight benefit of the titanium and composite options make them strong candidates for airframe design.

The optimum placement for a curved member is in a volume constrained area that allows for a long narrow mechanism to provide preload for the closure of a rigid member and allows for an expanded volume to move the rigid member into. The curved member works with a hinge or pivot point to help control the path of the rigid member as it is moved away from the frame. The design space allows for the attachment of the curved member to the rigid member at one end, and the attachment of the curved member at the other end to the frame and a reaction guiding element.

The reaction guiding element can be any element that can both restrict the free end of the curved member to follow a constrained path as the curved member returns to its free state and provide a surface against which the free end can react. As will be illustrated, typical reaction guiding elements may be a slot, a linkage or a reaction plate. For clarity, like elements will have the same reference numbers as assigned inFIGS.1A-1Dfor the generic reaction guiding element. Elements specific to the embodiment of the reaction guiding element will be assigned new reference numbers.

Referring now toFIGS.2A-2B, a mechanism200includes a reaction guiding element in the form of a slot202formed on rigid member100or alternatively on frame104. The slot202can be formed by either removing material from or adding it to the rigid member100(or frame104). The slot202can be linear or curved. It is understood that the slot202can be connected to or a part of the rigid member100or the frame104. In the closed-state, the second end116of curved member108is pinned in one end of slot202and attached to frame104by locking mechanism112with load105, and the first end114of the curved member108is pinned to the rigid member100. This stretches and straightens the curved member108that induces a tensile load which stores energy in the straightened member108. This causes the frame104to produce a reactive force111into rigid member100and pivot point102produces a pivot reaction113. This results in moment118, causing the rigid member100to be preloaded and closed to the frame104. When latching mechanism112is released, the freed or second end116of the curved member108follows slot202along a constrained path. As the curved member108returns towards its original curvature and contacts and reacts with frame104at point119with force115, the second end116of curved member108reacts with load121against a surface of slot202and the rigid member100reacts at pivot point102with a reactionary force113. This results in moment120, which opens the rigid member100, rotating about pivot point102, with respect to the frame104.

Referring now toFIGS.3A-3B, a mechanism300includes a reaction guiding element in the form of a linkage302and a stop304formed on rigid member100or alternatively on frame104. Linkage302can be any member that joins elements or members together typically with a pinned or multiple pinned ends. The joining areas are typically distanced apart in space. The joining allows for the rotation of the members in one or more directions relative to each other while constraining the path that the member(s) can move on with respect to the other member(s). The second end116of curved member108is pinned to the free end of linkage302. In the closed-state, linkage302is rotated away from the pinned first end114of curved member108and secured to frame104by locking mechanism112with load105, and the first end114of the curved member108is pinned to the rigid member100. This stretches and straightens the curved member108that induces a tensile load which stores energy in the straightened member108. This causes the frame104to produce a reactive force11into rigid member100and pivot point102produces a pivot reaction113. This results in moment118, causing the rigid member100to be preloaded and closed to the frame104. When latching mechanism112is released, curved member108releases its stored energy and moves the second end116whose path is constrained by linkage302. As the curved member108returns towards its original curvature and contacts and reacts with frame104at point119with force115the second end116of curved member108reacts with load121against linkage302and the rigid member100reacts at pivot point102with a reactionary force113. This results in moment120and linkage302rotating until it contacts stop304at the open-state of rigid member100and opens the rigid member100, rotating about pivot point102, with respect to the frame104.

Referring now toFIGS.4A-4B, a mechanism400includes a reaction guiding element in the form of a reaction plate402formed on rigid member100or alternatively on frame104. A reaction plate is a surface, flat or not flat, that allows for any member to push against it. It provides a reactionary force in one or more directions and does not typically restrain rotation of the member(s) reacting against it. In the closed-state, the second end116of curved member108is held against reaction plate402and attached to frame104by locking mechanism112with load105, and the first end114of the curved member108is pinned to the rigid member100. This stretches and straightens the curved member108that induces a tensile load which stores energy in the straightened member108. This causes the frame104to produce a reactive force111into rigid member100and pivot point102produces a pivot reaction113. This results in moment118, causing the rigid member100to be preloaded and closed to the frame104. When latching mechanism112is released, the freed or second end116of the curved member108reacts against the reaction plate402along a constrained path. As the curved member108returns towards its original curvature and contacts and reacts with frame104at point119with force115the second end of curved member108reacts with load121against the surface of reaction plate402and the rigid member100reacts at pivot point102with a reactionary force113. This results in moment120, which opens the rigid member100, rotating about pivot point102, with respect to the frame104.

Referring now toFIGS.5,6A-6C and7A-7C, a multi-stage missile500is provided with four fairings502to reduce aerodynamic drag where Stage Y504separates from Stage X506. A mechanism508of the type previously described including a slot520as the reaction guiding feature is configured to preload each fairing502against airframe512in a closed-state and when commanded to rotate fairing502about pivot point514away from the airframe512. Each of the four fairings502may remain attached to the previous stage506or be jettisoned separately from the stage506.

In an embodiment, mechanism508includes a curved member518that has a non-zero curvature in its originally manufactured or free-state (no stored energy), a reaction guiding element in the form of a slot520and a latch mechanism522such as a bolt cutter, explosive bolt, frangible bolt, explosive nut, separation nut or pulled pin. Curved member518has a first end524that is pinned to fairing502at a point offset from pivot point514and a second end526in slot520.

Latch mechanism522is configured to initially secure the second end526of the curved member518at one end of slot520and to the airframe512at a position offset from the pivot point514to put the curved member518under tension thereby straightening the curved member518to produce a first moment528in a rotational direction that preloads the fairing502against the airframe512in the closed-state. The airframe produces a reactionary force535into fairing502and pivot point514produces a pivot reaction537. In this example, latch mechanism522includes a tension bolt523that secures second end526to airframe512and a bolt cutter525. Note, “straightening” the curved member does not mean that the curved member becomes straight, merely that it is put under tension to reduce the curvature of the member. As shown, in this embodiment in the closed-state, the curved member518does not contact frame512, instead there is a gap between curved member518and the frame512. Alternately, curved member518could touch the frame512having the possible beneficial effects of absorbing shock or reducing lag time when released.

Latch mechanism522is configured to, when commanded, cause the bolt cutter525to break the tension bolt523which releases the second end526of the curved member518to allow the second end526to move within slot520, along a constrained path, to release tension in the curved member518and allow the return of the curved member518towards its non-zero curvature in the free state. The fairing502reacts with a reactionary load537at pivot point514and the curved member518reacts with airframe512at a position529offset from the pivot point514, where the curved member518contacts the airframe512producing a frame reactionary force539on the curved member518, reacts with the fairing502at the pinned first end524producing a reaction load541and reacts with a surface of slot520at free second end526producing a reaction load543to produce a second moment530in a second rotational direction opposite the rotational direction of the first moment528to rotate the fairing502about the pivot point514away from the airframe512. Curved member518must contact airframe512prior to reaching its free-state such that the curved member518retains energy to react with the frame512. In flight, once fairing502is opened to form a gap between the fairing and airframe512, airflow545will increase the rotational moment to fully open fairing502.

In the closed-state, the force of the latch mechanism522pulling the curved member518in one direction, combined with spacing of the pivot point514and its reactionary loads537away from a latching force vector547causes a couple to form between the two vectors, resulting in the moment528that causes the fairing502via the curved member518to be pulled against the airframe512and the airframe512to react against the fairing502with a reactionary load535resulting in the fairing502being preloaded into the closed position. Preloading the fairing502can mitigate gapping problems due to bending or flexure of the airframe512in flight that could prematurely open the fairing502.

To release the fairing502to the open-state, the force vector539of the airframe512reacting against the curved member518, combined with the spacing of the point of contact529away from the pivot point514and reactionary force vector537, results in force vectors that form a moment530between the two vectors causing the fairing502to rotate and open with respect to the airframe512. As the curvature of the curved member518increases, the fairing502will continue to open with respect to the airframe512.

Referring now toFIG.8, in an embodiment a mechanism800may include a plurality of curved members802that are laminated to form a set of parallel curved members. Each curved member802is suitably the same material and thickness or varying materials and thicknesses. The curved members802are joined together by hardware(s)804to form a single curved member806. One end808of the curved member set, suitably the longest or “main” curved member, is pinned to the rigid member and the other end809of the curved member set is in or on a reaction guiding element810and coupled via latch mechanism812to the frame. A single curved member will have a maximum allowable deflection of “X” and result in a stored energy of “Y”. This maximum deflection will be defined by taking the curved member material up to its maximum bending limit while not exceeding its elastic limit. Once the elastic limit is exceeded the energy is not stored but transfers into heat and plastic (permanent) deformation. If 4 curved members are employed in a parallel stack the deflection will be “X” still, but the stored energy will be 4 X Y because the integrated force will be four times greater.

With a single curved member 4 times the thickness the allowable deflection will be far less because the increased moment of inertia increases by a cube of the thickness. This reduction in deflection may not be desirable for the operation of the system. Tuning the force profile over the spring deflection will provide the design space to optimally tune said system. A single high spring rate curved member may be more or less desirable for the application versus a softer spring comprised of multiple springs with greater deflection.

The force vectors illustrated in the Figures are for illustrative purposes and may in alternate embodiments act in a different or opposite direction than shown. It is assumed that some vectors shown may be ‘negative’ vectors depending on the application and geometry of the applied embodiment.

While several illustrative embodiments of the disclosure have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Such variations and alternate embodiments are contemplated, and can be made without departing from the spirit and scope of the disclosure as defined in the appended claims.