Patent Description:
Hinges may be defined as a mechanical bearing that connects two solid objects, typically allowing only a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation, all other translations or rotations being prevented, and thus a hinge has one degree of freedom. The angle of rotation is typically limited by an external stop that impedes the rotation of one of the solid objects, the other solid object typically being fixed.

Certain aerodynamic bodies include elements such as optical windows or domes, air inlets etc. that need to be protected prior to flight, at launch or for some portion of flight before the elements are operational. A cover may be secured to the aerodynamic body to protect the element. At launch or later in flight, the cover is released. These systems typically use the aerodynamic forces caused by airflow into the body that produces forces radially outward on the cover to deploy and release the cover. In some cases, this occurs immediately after launch. In other cases, a mechanism secures the cover until it is released allowing the airflow to deploy the cover.

<CIT> entitled "Jettisonable Protective Element" discloses a number of embodiments in which a detachable hinge is configured to control the deployment of a cover from an aerodynamic body. As shown in <FIG> and described at col. <NUM>, line <NUM> to col. <NUM>, line <NUM>, the hinge <NUM> can be of an asymmetric ball in socket configuration. When the cover rotates to a predetermined angle, the ball element frees from the socket, thus enabling spontaneous disassembly of the hinge and detachment of the cover. Such a ball and socket hinge may have reliability issues related to either thermal heating, corrosion or manufacturing tolerances. Furthermore, the socket remains after detachment and may create localized hot spots or disturbances of the boundary layer of airflow over the aerodynamic body. As shown in <FIG>-4e and described at col. <NUM>, lines <NUM> to <NUM>, another embodiment of a hinge breaks at a structurally weakened region formed in the cover when the cover strikes a stoppage element positioned on the aerodynamic body. As shown in <FIG> and described at col. <NUM>, line <NUM> to col. <NUM>, line <NUM>, another embodiment of a hinge breaks at shearable pin along the rotation axis of the hinge when the cover strikes the stoppage element positioned on the aerodynamic body. The stoppage elements that limit the angle of rotation are positioned external to the hinge and offset from the axis of rotation. The load is transferred into cantilevered bending and dumped into the structurally weakened region (e.g., the slit of shearable pin) to shear off the cover. This places the breakage point in the primary flow path of an air-breathing system such as a turbine, RAM or SCRAM jet resulting in risk of damage to critical components from a Foreign Object Debris (FOD) perspective. Furthermore, the configuration of the stoppage elements increases the effective size of the detachable hinge and affects the outer mold line (OML) of the aerodynamic body, both before and after detachment of the cover.

Aspects of the invention are set out in the independent claims <NUM>, <NUM> and <NUM>.

The present invention relates to a hinge in which internal on-axis stopping mechanisms cause the hinge to shear and break at an on-axis weakened region of the hinge when rotation of the hinge reaches a predetermined angle with a specified torsional load. The on-axis configuration is compact, has minimal impact on the OML of the object to which it is mounted both pre and post detachment and allows for accurate tailoring of the load that will detach the hinge.

A hinge comprises first and second hinge plates configured for attachment to first and second solid objects, respectively. An on-axis member extends from the first hinge plate along an axis of rotation into a thru hole in the second hinge plate. A force exerted on the second solid object rotates the second solid object around the axis of rotation. The on-axis member includes a stopping feature and a weakened region positioned between the first hinge plate and the stopping feature. The second hinge plate includes a complementary stopping feature configured in the thru hole to engage the on-axis member's stopping feature at a predetermined angle of rotation to produce a torsional load on the on-axis member that creates torsional shear of the on-axis member at the weakened region to detach the hinge and remove the second solid object from the first solid object. The weakened region may, for example, constitute a smaller diameter region of the member, a slit or aperture formed in the member or with varying material properties.

The second solid object may be a cover that is permanently detached to uncover a previously covered area.

The covered area may include a protected element within the first solid object. For example, aerodynamic bodies such as missiles, rockets, guided artillery shells, UAVs, drones, manned aircraft or spacecraft may include protected elements such as optical sensing systems, air inlets or the like that must be protected in flight until those elements are operational.

In an airbone platform, a cover is reversibly secured to an aerodynamic body to protect a protected element from an external environment. A releasing mechanism (e.g., a pyrotechnic or piston actuator) is provided for at least partially detaching the cover from the aerodynamic body. A securing assembly secures the cover to the aerodynamic body. The securing assembly includes the hinge for connecting a first end of the cover to a first region of the aerodynamic body with a releasable element (e.g., tension screws, bands or other mechanically connected element) securing a second end of the cover to a second region of the aerodynamic body. The hinge is configured such that when the second end of the cover separates from the second region of the aerodynamic body in flight, a force (e.g., airflow or as provided by the releasing mechanism) exerted on the cover rotates the cover about an axis of rotation to engage the hinge's internal complementary stopping features at a predetermined angle thereby producing a torsional load that shears the hinge at the on-axis weakened region to release the cover. The hinge is compact and provides minimal impact on the OML of the aerodynamic body either pre or post-detachment.

The hinge may be designed in different ways reflecting varying degrees of integration of its component elements and with the solid objects to which it is attached. Different configurations may be selected and possibly combined depending upon the application.

In one configuration, the stopping feature is a discrete component fastened to the end of the on-axis member (e.g. via a fastener). The hinge includes a load transfer interface (e.g., a plurality of shear pins or a splined interface) that couples the stopping feature to the on-axis member to transfer the torsional load created by the engagement of the stopping features to the on-axis member to shear the on-axis member at the weakened region. The discrete component may include a full diameter region equal to the diameter of the thru hole in rotational engagement with the thru hole at the load transfer interface. The on-axis member may include an integrally formed full diameter region, adjacent the weakened region, which is coupled to the full diameter region of the discrete component via the load transfer interface.

In another configuration, at least one or both of the first and second hinge plates are integrally formed with the first and second solid objects, respectively. At least the weakened region of the on-axis member may be integrally formed with the first hinge plate and first solid object. The entire on-axis member may be integrally formed with the first hinge plate and first solid object.

In another configuration, the on-axis member is integrally formed to include the weakened region and the stopping feature. In this case, the torsional load created by the engagement of the complementary stopping features is applied directly to the weakened region.

In another configuration, the on-axis member, integrally formed or discretely joined, may include a full diameter region equal to the diameter of the thru hole in rotational engagement with the thru hole. In one case, the stopping feature is offset axially from the full diameter region to engage the complementary stopping feature. In another case, the stopping feature is formed in the full diameter region to engage the complementary stopping feature.

Features and advantages of the invention 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:.

The present invention provides a hinge in which internal on-axis stopping mechanisms cause the hinge to shear and break at an on-axis weakened region of the hinge when rotation of the hinge reaches a predetermined angle with a specified torsional load. The on-axis configuration is compact, has minimal impact on the OML of the object to which it is mounted both pre and post detachment and allows for accurate tailoring of the load that will detach the hinge.

Although generally desirably in most applications, these features are of particular importance to aerodynamic bodies such as missiles that travel at very high speeds. Space on or in an aerodynamic body of this type is at a premium. The on-axis configuration of the hinge is very compact, its footprint being only that of the hinge components that support rotation of the cover. Because the aerodynamic body travels at high speeds its OML is carefully designed for aerodynamics, to limit local thermal effects and disruption of the boundary layer of airflow over the body. Because all aspects of the hinge are internal, the hinge itself creates minimal impact on the OML either pre or post-detachment of the cover. Furthermore, the on-axis hinge design limits FOD in the primary flow path of an air-breating system if used to cover an air intake, for example.

A hinge comprises first and second hinge plates configured for attachment to first and second solid objects, respectively. An on-axis member extends from the first hinge plate along an axis of rotation into a thru hole in the second hinge plate. A force exerted on the second solid object rotates the second solid object around the axis of rotation. The on-axis member includes a stopping feature and a weakened region positioned between the first hinge plate and the stopping feature. The second hinge plate includes a complementary stopping feature configured in the thru hole to engage the on-axis member's stopping feature at a predetermined angle of rotation to produce a torsional load on the on-axis member that creates torsional shear of the on-axis member at the weakened region to detach the hinge and remove the second solid object from the first solid object. The weakened region may, for example, constitute a smaller diameter region of the member, a slit or aperture formed in the member or varying material properties.

In different embodiments, the second solid object may be a cover that is permanently detached to uncover a previously covered area. In certain embodiments, the covered area may include a protected element within the first solid object. For example, aerodynamic bodies such as missiles, rockets, guided artillery shells, UAVs, drones, manned aircraft or spacecraft may include protected elements such as optical sensing systems, air inlets or the like that must be protected in flight until those elements are operational.

In an airborne platform, a cover is reversibly secured to an aerodynamic body to protect a protected element from an external environment. A releasing mechanism (e.g., a pyro technic or piston actuator for controlled release or springloaded or airflow for release at launch) is provided for at least partially detaching the cover from the aerodynamic body. A securing assembly secures the cover to the aerodynamic body. The securing assembly includes the hinge for connecting a first end of the cover to a first region of the aerodynamic body with a releasable element (e.g., tension screws, bands or other mechanically connected element) securing a second end of the cover to a second region of the aerodynamic body. The hinge is configured such that when the second end of the cover separates from the second region of the aerodynamic body in flight, a force (e.g., airflow or as provided by the releasing mechanism) exerted on the cover rotates the cover about an axis of rotation to engage the hinge's internal complementary stopping features at a predetermined angle thereby producing a torsional load that shears the hinge at the on-axis weakened region to release the cover. The hinge is compact and provides minimal impact on the OML of the aerodynamic body either pre or post-detachment.

The hinge may be designed in different ways reflecting varying degrees of integration of its component elements and with the solid objects to which it is attached. Different configurations may be selected and possibly combined depending upon the application. Without loss of generality, a hinge <NUM> using discrete components to secure and then controllably detach a cover <NUM> from a missile <NUM> will be presented with reference to <FIG>, <FIG>, <FIG>, <FIG> and <FIG>.

Missile <NUM> includes an aerodynamic body <NUM>, a protected element <NUM> within the aerodynamic body and cover <NUM>, reversibly secured to the aerodynamic body, for protecting the protected element from an external environment. A releasing mechanism <NUM> such as a pyrotechnic actuator or a piston actuator is configured to at least partially detach the cover from the aerodynamic body. A securing assembly <NUM> secures the cover to the aerodynamic body. The securing assembly <NUM> includes the hinge <NUM> for connecting a first end <NUM> of the cover to a first region <NUM> of the aerodynamic body, and a releasable element <NUM> such as tension screws, bands or other mechanically connected element securing a second end <NUM> of the cover to a second region <NUM> of the aerodynamic body. Hinge <NUM> is configured such that when the second end <NUM> of the cover separates from the second region <NUM> of the aerodynamic body when the missile is in flight, a force <NUM> exerted on the cover rotates the cover about an axis of rotation <NUM> before detaching the hinge <NUM>, thereby removing the cover <NUM> from missile <NUM>. Force <NUM> may, for example, be provided by the releasing mechanism <NUM> or by airflow over the aerodynamic body.

In this discrete configuration, hinge <NUM> includes a first hinge plate <NUM> attached to the aerodynamic body <NUM>. An on-axis member <NUM> extends from the first hinge plate <NUM> along the axis of rotation <NUM> aligned with a first thru hole <NUM> in cover <NUM>. The on-axis member includes a full diameter region <NUM> equal in diameter to the first thru hole <NUM> in the cover and a reduced diameter weakened region <NUM> positioned between the first hinge plate <NUM> and the full diameter region <NUM>. A hard stop <NUM> includes a full diameter region <NUM> fastened to the end of the full diameter region <NUM> of the on-axis member via a fastener <NUM> and a stopping feature <NUM>. Full diameter region <NUM> is in rotational engagement with the first thru hole <NUM> in the cover such that the force <NUM> rotates the cover around the axis of rotation.

A load transfer interface, shown here as a plurality of shear pins <NUM>, couples the full diameter region <NUM> of the hard stop <NUM> to the full diameter region <NUM> of the on-axis member <NUM>. The interface serves to transfer a torsional load created when the complementary stopping features are engaged to the weakened region of the on-axis member. The cumulative shear strength of the interface, here the plurality of shear pins, must be greater than the shear strength of the weakened region. For example, the weakened region may exhibit a shear of <NUM> lbf (pound feet) while the pins cumulative strength is <NUM> Ibf. Under more strenuous flight conditions, the weakened region may exhibit a torsional shear of <NUM> lbf while the pins cumulative strength is <NUM> Ibf. This can be achieved by varying the diameter of the weakened region or by maintaining the same geometry but varying the material properties of the on-axis member versus the hard stop. Note, the fastener <NUM> that fastens the hard stop to the on-axis member has minimal affect on load transfer, its purpose is to secure the hard stop to the on-axis member.

A second hinge plate <NUM> is positioned in a recess <NUM> in cover <NUM> and attached (clamped) to the cover via fasteners <NUM> that engage a ring assembly <NUM> positioned on the inner surface of the cover opposite the second hinge plate. Ring assembly <NUM> includes a floating nut plate <NUM> that is attached to a ring <NUM> via fasteners <NUM>. Second hinge plate <NUM> has a second thru hole <NUM> aligned to the first thru hole <NUM>. The second hinge plate has a complementary stopping feature <NUM> configured in the second thru hole <NUM> to engage the hard stop's stopping feature <NUM> at a predetermined angle of rotation to produce moment <NUM> about the axis of rotation <NUM> to transfer a torsional load <NUM> thru the load transfer interface <NUM> to shear the on-axis member <NUM> at the reduced diameter weakened region <NUM> to detach the hinge <NUM> and remove the cover <NUM> from the aerodynamic body <NUM> leaving the first hinge plate <NUM> and a small proturbance <NUM> (what remains of the weakened region <NUM>) attached to the aerodynamic body.

Referring specifically to <FIG>, hinge <NUM> is assembled to attach cover <NUM> to aerodynamic body <NUM> by attaching the first hinge plates <NUM> to the aerodynamic body. Ring assembly <NUM> is placed on the on-axis member <NUM> that extends from the first hinge plates along the axis of rotation. Cover <NUM> is positioned to align thru hole <NUM> with the on-axis member <NUM> and axis of rotation <NUM> as shown in <FIG>. The second hinge plate <NUM> is placed in recess <NUM> and fasteners <NUM> are inserted through the second hinge plate to engage ring assembly <NUM> to clamp the second hinge plate <NUM> to cover <NUM> as shown in <FIG>. Lastly, hard stop <NUM> is coupled to on-axis member <NUM> via shear pins <NUM> and fastener <NUM> between its full diameter region <NUM> and the on-axis member full diameter region <NUM> as shown in <FIG>.

Referring specifically to <FIG>, <FIG> and <FIG>, hinge <NUM> is engaged in flight to controllably release and permanently detach cover <NUM>. As shown in <FIG>, hinge <NUM> and cover <NUM> are secured in a closed or stowed position at <NUM>° of rotation. The second end <NUM> of the cover is secured to the second region <NUM> of the aerodynamic body <NUM> to protect the protected element <NUM> (e.g. an air intake). At <NUM>° of rotation, the cover's complementary stopping feature <NUM> does not engage the hard stop <NUM>. As shown in <FIG>, the releasing mechanism (pyrotechnic actuator) <NUM> has separated the releasable elements <NUM> (tension screws) to partially detach cover <NUM> from aerodynamic body <NUM>. The airflow over the aerodynamic body produces forces <NUM> that are exerted on cover <NUM> causing cover <NUM> to rotate about axis of rotation <NUM> to <NUM>° of rotation at which point the cover's complementary stopping feature <NUM> has engaged the hard stop <NUM> producing a moment <NUM> about the axis of rotation, which in turn produces torsional load <NUM>. Shear pins <NUM> transfer the torsional load <NUM> to the reduced diameter weakened region <NUM> of the on off-axis member. As shown in <FIG>, hinge <NUM> has sheared off at the reduced diameter weakened region <NUM> leaving only a small proturbance <NUM> on the first hinge plate <NUM> attached to aerodynamic body <NUM>.

Referring now to <FIG>, in an embodiment of a hinge <NUM> a first hinge plate <NUM> and a portion of an on-axis member <NUM> including a reduced diameter weakened region <NUM> and a full diameter region <NUM> are integrally formed with the aerodynamic body and a second hinge plate <NUM> including a complementary stopping feature <NUM> is integrally formed in a thru hole <NUM> in a cover <NUM>. As before, cover <NUM> is positioned to align thru hole <NUM> with on-axis member <NUM> whose full diameter region <NUM> nearly contacts the inner surface of the cover. A hard stop <NUM> is attached is attached to on-axis member <NUM> via fastener <NUM>. In this example, the load transfer interface is implemented with a splined interface <NUM> formed on the opposing surfaces of the on-axis member <NUM> and the hard stop <NUM>.

Referring now to <FIG>, in an embodiment of a hinge <NUM>, an on-axis member <NUM> is integrally formed to include a reduced diameter weakened region <NUM>, a full diameter region <NUM> and a stopping feature <NUM>. In one configuration, a thru hole <NUM> in a cover <NUM> is aligned to a mounting feature <NUM> on the aerodynamic body. The on-axis member <NUM> is inserted in the through hole to engage mounting feature <NUM>. A complementary stopping feature <NUM> may be formed either in a hinge plate attached to cover <NUM> or integrally in thru hole <NUM> in the cover as shown in the drawing. An integrally formed on-axis member does not require a load transfer interface to transfer the torsional load produced by engagement of the complementary stopping features to the reduced diameter weakened region.

The on-axis hinge includes both a full diameter region in rotational engagement with a thru hole in the cover/hinge plate to provide reliable and stable rotation of the cover about the axis of rotation away from the aerodynamic body and complementary stopping features formed on the on-axis member and in the thru hole that engage at a predetermined angle and shear the hinge to permanently detach the cover. Up to this point, the complementary stopping features are physically offset axially from the full diameter region of the on-axis member and the thru hole and functionally separately. However, the complementary stopping features may be incorporated into the full diameter region of the on-axis member and the thru hole. In so doing, a portion of the <NUM>° degrees of possible rotational engagement between the full diameter region of the on-axis member and the inner surface of the thru hole must be sacrificed. How much of the360° degrees must be sacrificed depends both on the predetermined angle of rotation at which the complementary stopping features are engaged and the geometry of those features. This may be implemented in either a discrete configuration in which a hard stop is pinned to the on-axis member or in which the hard stop is integrally formed with the on-axis member.

Referring now to <FIG>, in an embodiment of a hinge <NUM>, an on-axis member <NUM> includes a reduced diameter weakened region <NUM> and a full diameter region <NUM>. A hard stop <NUM> is coupled to the on-axis member via shear pins <NUM> and fastener <NUM>. Hard stop <NUM> includes a full diameter region <NUM> in which a quadrant has been removed to form a stopping feature <NUM>. A complementary stopping feature <NUM> is formed in a wall of a full diameter thru hole <NUM> to engage stopping feature <NUM> at a predetermined angle.

Claim 1:
A hinge (<NUM>), comprising:
a first hinge plate (<NUM>) configured for attachment to a first solid object (<NUM>);
an on-axis member (<NUM>) that extends from the first hinge plate along an axis of rotation (<NUM>), said on-axis member including a stopping feature (<NUM>) and a weakened region (<NUM>) positioned between the first hinge plate and the stopping feature; and
a second hinge plate (<NUM>) configured for attachment to a second solid object (<NUM>), said second hinge plate having a thru hole (<NUM>) for receiving the on-axis member such that a force exerted on the second solid object rotates the second solid object around the axis of rotation, said second hinge plate having a complementary stopping feature (<NUM>) configured in said thru hole to engage the on-axis member's stopping feature at a predetermined angle of rotation to produce a torsional load on the on-axis member that shears the on-axis member at the weakened region to detach the hinge and remove the second solid object from the first solid object.