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TECHNICAL FIELD 
       [0001]    This invention relates generally to locking hinges that are equipped with spring-driven pre-loading features. More specifically, this disclosure relates to locking hinges that may be used on spacecraft to allow antenna booms or other deployable structures to be coupled to the spacecraft main body via a hinged connection that, after deployment, may be locked and pre-loaded to prevent or reduce gapping or compliance in the hinge interface. 
       BACKGROUND OF THE INVENTION 
       [0002]    The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services. Spacecraft often include various deployable structures, e.g., equipment booms, solar arrays, antenna reflectors, antenna masts, etc. Such structures may, for example, often be folded flat against a side of the spacecraft during launch and may then subsequently be deployed using, for example, hinged connections when the spacecraft is on-orbit. 
         [0003]    Because of the large distances involved, small misalignments in such a hinge may have significant repercussions in overall system performance. For example, a 0.1 degree misalignment in an antenna reflector for a satellite at an altitude of 37,000 km may cause the resulting terrestrial antenna illumination area to shift by nearly 65 km. 
         [0004]    There is thus a need for hinged interfaces for use in satellites that have anti-compliance or anti-gapping capabilities when in the hinge-closed state. 
       SUMMARY OF INVENTION 
       [0005]    The systems, methods and devices of the disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein. One innovative aspect of the subject matter described in this disclosure can be implemented in a variety of ways. 
         [0006]    The present inventor has appreciated that a latching hinge that includes a mechanism that causes a compressed spring load to be applied to the latching components after the hinge has been closed and is in the latched state may be used to provide a low-compliance deployment hinge for use in spacecraft or other systems, e.g., a hinge that exhibits a reduced potential for gapping movement, i.e., movement in the hinge that results in a gap opening up between the hinge components. While the inventor has presented several variants of such locking hinges herein, the general concept of using a spring-loaded tensioning device in such a manner may be applied to a variety of other latching hinge designs and all such variants are considered to be within the scope of this disclosure. 
         [0007]    In some implementations, a latching hinge is provided that includes a first member, a second member rotatably coupled to the first member about a hinge pivot, a latch link connected with the first member, a latch hook connected with the second member, a spring-loaded tensioning device, and a trigger mechanism. The first member and the second member may be configured to be transitioned between a hinge-open state and a hinge-closed state by rotating one of the first member and the second member with respect to the other of the first member and the second member about the hinge pivot; at least a portion of at least one of the latch link and the latch hook may be configured to move relative to the first member and the second member, respectively, such that the latch hook and a latch portion of the latch link latch together as the first member and the second member are transitioned into the hinge-closed state. The latch link and the latch hook may also prevent the first member and the second member from being transitioned into the hinge-open state from the hinge-closed state when the latch portion of the latch link and the latch hook are latched together. The spring-loaded tensioning device in such a device may be configured to be transitioned between a first compressed state and a second compressed state; a tensile load may be induced in the latch link and the latch hook when the spring-loaded tensioning device is in the second compressed state and the latch portion of the latch link and the latch hook are latched together. The trigger mechanism (i) may be configured to be transitioned between a untriggered state and a triggered state, (ii) may maintain, in the untriggered state, the spring-loaded tensioning device in the first compressed state, (iii) may allow, in the triggered state, the spring-loaded tensioning device to transition from the first compressed state to the second compressed state, and (iv) may be configured to transition from the untriggered state to the triggered state after the latch portion of the latch link and the latch hook have latched together. 
         [0008]    In some such implementations, the latch hook may be rotatable about a first pivot and the spring-loaded tensioning device may be configured to exert a first compressive load on a portion of the latch hook to develop a torque about the first pivot when transitioning from the first compressed state to the second compressed state. In such implementations, the latch hook may be drawn into contact with the latch portion of the latch link responsive to the developed torque. In some further such implementations, the latching hinge may further include a latch link bias spring that may be configured to bias the latch link towards the position the latch link is in with respect to the first member when the latch link and the latch hook are latched together. In yet some further such implementations, the latch link may be configured to rotate about a latch link pivot, the latch portion of the latch link may encounter a sloped surface of the latch hook as the first member and the second member transition from the hinge-open state to the hinge-closed state, and the sloped surface of the latch hook may be oblique to the direction along which the tensile load is induced and may engage with the latch portion so as to cause the latch link to rotate about the latch link pivot and deflect the latch link bias spring as the first member and the second member transition into the hinge-closed state. 
         [0009]    In some implementations of the latching hinge, the spring-loaded tensioning device may include a linear spring such as a coil spring or a plurality of Belleville washers stacked on a common guide that passes through the center of each Belleville washer. In some such implementations, the spring-loaded tensioning device may have a spring extension axis aligned with the direction along which the tensile load is induced in the latch link and the latch hook when the spring-loaded tensioning device is in the second compressed state and the latch portion of the latch link and the latch hook are latched together. In some alternative such implementations, the spring-loaded tensioning device may have a spring extension axis perpendicular to the direction along which the tensile load is induced in the latch link and the latch hook when the spring-loaded tensioning device is in the second compressed state and the latch portion of the latch link and the latch hook are latched together. 
         [0010]    In some implementations of the latching hinge, the latch link may be movably connected with a latch link rotation arm, the latch link rotation arm may be configured to rotate about a first pivot, the spring-loaded tensioning device may be configured to exert a force on a portion of the latch link rotation arm to generate a torque about the first pivot when transitioning from the first compressed state to the second compressed state, and the latch portion of the latch link may be drawn into contact with the latch hook responsive to the torque. 
         [0011]    In some implementations of the latching hinge, the trigger mechanism may include a lever arm component configured to rotate about a fulcrum, a trigger, and a release mechanism. In such implementations, the spring-loaded tensioning device may exert a first compressive load on a portion of the latch hook in the first compressed state and a second compressive load on a portion of the latch hook in the second compressed state, the latch hook may contact the lever arm component and transfer the first compressive load from the spring-loaded tensioning device to a first contact zone of the lever arm component and along a first peak magnitude vector when the trigger mechanism is in the untriggered state and may transfer the second compressive load to the latch portion of the latch link when the trigger mechanism is in the triggered state. In such implementations, the release mechanism may be configured to contact the lever arm component at at least one second contact zone and apply a third compressive load on the at least one second contact zone and along a second peak magnitude vector when the spring-loaded tensioning device is in the untriggered state, and to release the lever arm component by removing the third compressive load responsive to engagement with a portion of the first member. 
         [0012]    In some implementations of the latching hinge, the release mechanism may be provided by at least one spring arm with a detent. The detent may engage with the lever arm component at the second contact zone and may resist movement of the lever arm component due to the first compressive load when engaged. The trigger may be configured to contact the at least one spring arm and to deflect the at least one spring arm as the first member and the second member are transitioned into the hinge-closed state, and the deflection of the at least one spring arm by the trigger may then cause the detent to move such that the detent releases the lever arm. 
         [0013]    In some implementations of the latching hinge, the shortest distance A between the first peak magnitude vector and the fulcrum may be at least an order of magnitude less than the shortest distance B between the second peak magnitude vector and the fulcrum. In some such implementations, the shortest distance A between the first peak magnitude vector and the fulcrum may be less than 1/50 th  of the shortest distance B between the second peak magnitude vector and the fulcrum. 
         [0014]    In some implementations of the latching hinge, the first compressive load may be approximately 1500 lbf±200 lbf, the second compressive load may be approximately 750 lbf±100 lbf, the third compressive load may be less than 10 lbf±1 lbf, and the tensile load may be 810 lbf±100 lbf. 
         [0015]    In some implementations of the latching hinge, the magnitude of the first compressive load may be multiplied by the ratio of a) the shortest distance C between the first pivot and the peak magnitude vector of the first compressive load to b) the shortest distance D between the first peak magnitude vector and the first pivot as the first compressive load is transferred to the first contact zone by the latch hook. In some such implementations, this ratio may be less than one. 
         [0016]    In some implementations of the latching hinge, the lever arm component may be a third-class lever configured to pivot about the fulcrum. 
         [0017]    In some implementations of the latching hinge, the latching hinge may also include a radial alignment feature pair including a concave conic surface and a complementary convex conic surface and two or more linear alignment feature pairs. Each linear alignment feature pair may include a concave prismatic surface and a complementary convex prismatic surface. In such implementations, one of the concave conic surface and the convex conic surface may be located on the first member and the other of the concave surface and the convex conic surface may be located on the second member such that the concave conic surface and the convex conic surface contact one another when the first member and the second member are in the hinge-closed state. Furthermore, one of the concave prismatic surface and the convex prismatic surface of each linear alignment feature pair may be located on the first member and the other of the concave prismatic surface and the convex prismatic surface of the linear alignment feature pair may be located on the second member such that the concave prismatic surface and the convex prismatic surface of each linear alignment feature pair contact one another when the first member and the second member are in the hinge-closed state. The concave prismatic surface and the convex prismatic surface of each linear alignment feature pair may also contact each other along surfaces that bracket an axis that passes through the center axis of the concave conic surface when the first member and the second member are in the hinge-closed state. 
         [0018]    In some such implementations, when the first member and the second member are in the hinge-closed state and the tensile load is induced in the latch link and the latch hook, the tensile load (a) draws the convex conic surface and the concave conic surface of the radial alignment feature pair into contact with one another and (b) draws the convex prismatic surface and the concave conic surface of each linear alignment feature pair into contact with one another. 
         [0019]    In some implementations of the latching hinge, the hinge pivot may include a radial clearance gap between portions of the hinge pivot that define the rotatable bearing interface provided by the hinge pivot. In such implementations, there is load transferred between the first member and the second member through the hinge pivot as the first member and the second member transition from the hinge-open state to the hinge-closed state, and there is no load transferred between the first member and the second member via the hinge pivot when the tensile load in the latch link and the latch hook is present. 
         [0020]    In some implementations, the latching hinge may be used to connect an extensible equipment boom with a spacecraft. In such implementations, the latching hinge may be in the hinge-open state when the extensible equipment boom is in the stowed state, and the latching hinge may be in the hinge-closed state when the extensible equipment boom is in the deployed state. 
         [0021]    Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures, unless otherwise noted, may not be drawn to scale. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  depicts an isometric view of an example latching hinge in a hinge-open state. 
           [0023]      FIG. 2  depicts an isometric view of the example latching hinge of  FIG. 3  in a hinge-closed state. 
           [0024]      FIG. 3  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in the hinge-open state. 
           [0025]      FIG. 4  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state approximately halfway between the hinge-open state and a hinge-closed state. 
           [0026]      FIG. 5  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state of transition from the hinge-open state to the hinge-closed state where a latch portion of a latch link has contacted a portion of the latch hook. 
           [0027]      FIG. 6  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state of transition from the hinge-open state to the hinge-closed state where the latch portion of the latch link has been deflected due to the portion of the latch hook. 
           [0028]      FIG. 7  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state of transition from the hinge-open state to the hinge-closed state where the latch link and the latch hook have latched together. 
           [0029]      FIGS. 8A and 8B  depict an example spring-loaded tensioning device using Belleville washers in two different states of compression. 
           [0030]      FIG. 9  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in the hinge-closed state. 
           [0031]      FIG. 10  depicts an isometric section view of the latching hinge of  FIGS. 1 and 2  in the hinge-open state. 
           [0032]      FIG. 11  depicts an isometric section view of the latching hinge of  FIGS. 1 and 2  during the transition between the hinge-open state and the hinge-closed state and after the latch link and the latch hook have latched. 
           [0033]      FIG. 12  depicts an isometric section view of the latching hinge of  FIGS. 1 and 2  in the hinge-closed state. 
           [0034]      FIG. 13  depicts a simplified diagram of a latching hinge with a spring-loaded tensioning device similar to the example shown in  FIGS. 2 through 12 . 
           [0035]      FIG. 14  depicts a simplified diagram of an alternative mechanism for a latching hinge with a spring-loaded tensioning device. 
           [0036]      FIG. 15  depicts a simplified diagram of another alternative mechanism for a latching hinge with a spring-loaded tensioning device. 
           [0037]      FIG. 16  depicts a simplified diagram of yet another alternative mechanism for a latching hinge with a spring-loaded tensioning device. 
           [0038]      FIG. 17  depicts a diagram of a release mechanism in an unreleased state. 
           [0039]      FIG. 18  depicts a diagram of the release mechanism of  FIG. 17  in a released state. 
           [0040]      FIG. 19  depicts a diagram of a release mechanism such as that pictured in  FIGS. 1 through 12  in an unreleased state. 
           [0041]      FIG. 20  depicts a diagram of the release mechanism of  FIG. 19  in a released state. 
           [0042]      FIG. 21  depicts a schematic of a spacecraft with an extensible equipment boom. 
           [0043]      FIG. 22  depicts a schematic of the spacecraft of  FIG. 21  with the extensible equipment boom in a deployed state. 
           [0044]      FIGS. 1 through 12  are drawn to scale within each Figure, although the Figures may vary in scale from Figure to Figure. 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    Specific exemplary embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0046]    It will be understood that when an element is referred to as being “connected” or “coupled” to or with another element, it may be directly connected or coupled to or with the other element, or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein in an electrical context may include wirelessly connected or coupled. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The symbol “/” may also be used as a shorthand notation for “and/or.” 
         [0047]      FIG. 1  depicts an isometric view of an example latching hinge in a hinge-open state. The latching hinge  100  may include two main parts: a first member  102  and a second member  104 . The first member  102  may be joined to the second member  104  via a hinge pivot  120  such that the first member  102  and the second member  104  may be rotated relative to each other about a hinge axis of the hinge pivot  120  so as to be transitionable between a hinge-open state, shown in  FIG. 1 , and a hinge-closed state, shown in  FIG. 2 . As will be discussed later, in some implementations, the hinge pivot  120  may be a “loose-fit” hinge interface with engineered-in radial compliance. As shown, the hinge pivot  120  includes various components, e.g., spring drums  172 , rotational dampers  170 , and various other components, either not shown or not indicated, that, in aggregate, may provide for rotational movement between the first member  102  and the second member  104 . 
         [0048]    The latching hinge  100  in this example is a spring-driven hinge, i.e., the first member  102  and the second member  104  are urged into the hinge-closed state from the hinge-open state by a deformed spring of some sort. In this particular example, two torsion springs  134  are used to apply a rotational moment about the hinge pivot  120  that will cause the first member  102  to rotate with respect to the second member  104 . This assumes that the second member  104  is fixed in space—the reverse arrangement is, of course, also possible. The torsion springs  134  may be constant-torque or near-constant torque springs, for example, having an average torque during hinge actuation that stays within ±10% of a given nominal torque value. 
         [0049]    The first member  102  and the second member  104  may also include various alignment features that act to ensure that the first member  102  and the second member  104  are correctly aligned with one another in the hinge-closed state. These alignment features may include a radial alignment feature with a concave conic surface  156  on the second member  104  and a complementary convex conic surface  156 ′ on the first member  102 . It is to be understood that the concave conic surface  156  may also be located on the first member  102  and the convex conic surface  156 ′ may correspondingly be located on the second member  104  in some implementations. The radial alignment feature may act to anchor the first member  102  in space relative to the second member  104  when the latching hinge  100  is in the hinge-closed state. In addition to the radial alignment feature, two or more linear alignment features, each with a concave prismatic surface  158  and a complementary convex prismatic surface  158 ′, may be located at other locations on the first member  102  and the second member  104 . The concave prismatic surfaces  158 , in this example, are symmetrical trapezoidal troughs with the trough axis passing through the center of the concave conic surface  156 , and the convex prismatic surfaces  158 ′, in this example, are matching symmetrical trapezoidal protrusions, although sized such that only the sloped sides of the trapezoidal cross-sections are in contact with one another when the concave prismatic surface  158  and the convex prismatic surface  158 ′ are in contact with one another; the same is true for the concave conic surface  156  and the convex conic surface  156 ′. This arrangement allows the concave prismatic surface  158  and the convex prismatic surface  158 ′ to slide relative to each other along an axis that passes through the radial alignment feature, which, for example, allows for independent expansion/contraction of the first member  102  and the second member  104  due to different amounts of thermal expansion arising from non-uniform temperature distributions in the latching hinge  100 . For example, the portion of the latching hinge that is attached to a spacecraft body may be exposed to heat that flows into it from the spacecraft body, and may thus be warmer than the portions of the latching hinge  100  that are further from the spacecraft body. 
         [0050]    Also visible in  FIG. 1  are various components that provide latching and preload-transfer functionality. For example, the first member  102  may include a latch link  108  that may have a latch portion  110 , in this case, a pin, although other designs may feature a different component or even a feature that provides similar functionality, as discussed herein, but that is an integral part of the latch link  108  rather than a separate component. The latch link  108  may be configured to rotate about a latch link pivot  124 , but may be urged to remain in the position shown by a latch link bias spring  132  or other device providing similar functionality. The first member  102  may also include a trigger  144 , which may be positioned so as to engage with a release mechanism  136  located on the second member  104 . 
         [0051]    The second member  104  may also include various components that provide latching and preload-transfer functionality. Visible in  FIG. 1  are part of a latch hook  106  and a lever arm component  116 . The latch hook  106  may be configured to engage with the latch portion  110  of the latch link  108 , thus providing a latch mechanism for the latching hinge  100 . A spring-loaded tensioning device, which is not visible in  FIGS. 1 and 2  but is detailed in various section views discussed later in this disclosure, may be configured to transfer a compressive load from a compressed spring, via various load-transfer mechanisms/components, to the latch hook/latch portion interface, thus causing a tensile load to be developed across the latch hook and latch link when the two components are in the latched state. This tensile load may, in turn, be resisted by compressive loads that are applied through the contact interfaces of the radial alignment feature and the linear alignment features. Thus, all or substantially all of the loads associated with the transferred pre-load may pass through the latch mechanism and the various alignment features provided. Other implementations, however, may omit the above-discussed alignment features and may, for example, feature simple, flat mating surfaces on the first member  102  and the second member  104  for compressive load transfer between the first member  102  and the second member  104 . 
         [0052]    In addition to the features discussed above, various other features are visible in the Figures discussed herein; the purposes or functions of these features are readily apparent, e.g., fasteners for joining two components together, lock rings for preventing axle components from sliding along their axes, holes for bolting the first member  102  or the second member  104  to other structures such as spacecraft bodies or equipment booms, etc. and are thus not described in detail. Other components that may be included in the latching hinge  100  may include rotational damper units that act to limit the rotational velocity of the first member  102  and the second member  104  (the cylindrical structures on the outer ends of the hinge pivot  120 ). 
         [0053]      FIGS. 3 through 9  depict section views of the latching hinge  100  at various points of transition between, and inclusive of, the hinge-open state and the hinge-closed state. For further understanding,  FIGS. 10 through 12  depict isometric section views that correspond with the views shown in  FIGS. 1, 7, and 9 , respectively. 
         [0054]      FIG. 3  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in the hinge-open state. As can be seen, many of the components discussed above with respect to  FIGS. 1 and 2  are visible in greater detail in  FIG. 1 , as well as many additional components that were not visible in  FIGS. 1 and 2 . 
         [0055]    For example, the spring-loaded tensioning device  114  is depicted. The spring-loaded tensioning device  114  may include a base  142  that may be fixed in space relative to the second member  104 . The base may, for example, be a threaded tube with a flanged end that interfaces with a spring of some sort. The spring, in this example, is provided by a plurality of conical washers, or Belleville washers, that are stacked on a guide of some sort. In this example, the guide is provided by a plunger  130 , which includes a shaft that is sized so as to be insertable through the center hole of each Belleville washer and that has larger-diameter end portion that is configured to bear against a portion of the latch hook  106 . The latch hook  106  may be configured to rotate about a first pivot  122 ; the force applied to the latch hook  106  by the plunger  130  may thus generate a moment in the latch hook  106  about the first pivot  122 . 
         [0056]    The Belleville washers may be stacked on the guide in alternating directions, e.g., with the cone angles of each pair of adjacent Belleville washes facing in opposite directions. When the plunger  130  is compressed into the base  142 , this causes the Belleville washers to flatten, i.e., the cone angle of the Belleville washers is reduced in response to the applied load. The Belleville washer stack shown in  FIG. 3  has been compressed by the plunger  130  to such an extent that each Belleville washer  128  has been flattened completely and looks, in cross-section, like a normal, flat washer. The base  142  may be held in place with respect to the second member  104  by two jam nuts that interface with the threaded portion of the base  142 . This allows the base position relative to the latch hook  106  along the spring extension axis to be fine-tuned. The plunger  130  may also have features, e.g., a threaded female hole on the end opposite the larger-diameter end portion, that allow a tool of some sort to be used to pull the plunger towards the base, thus compressing the spring, during installation and initial setup. It is to be understood that while the pictured implementation features a stack of alternating Belleville washers, it is also possible to achieve a similar effect with a stack of Belleville washers all oriented in the same direction or in a mixture of alternating and same directions. Alternating Belleville washers may be used to provide increased stroke length at the expense of force, and same-direction Belleville washers may be used to provide increased force at the expense of stroke length. It is also to be understood that other types of springs may be used in place of a Belleville washer stack, if desired—for example, a traditional coil spring may be used instead. While a linear spring is shown, similar functionality may be provided using other types of spring devices, such as torsion springs that are configured to generate the moment in the latch hook  106  about the first pivot  122 ). A “linear spring,” as used herein, refers to a spring that acts along a generally linear path and does not mean that the spring necessarily has a linear force/displacement curve; although such may be the case, linear springs may also have non-linear force/displacement curves. Such alternative implementations are also considered to be within the scope of this disclosure. 
         [0057]    The latch hook  106  may, as discussed above, be configured to rotate about the first pivot  122 . The latch hook  106  may also have a contact surface  112  that is designed to contact the latch portion  110  of the latch link  108  when the latching hinge  100  is in the closed state and an attempt is made to transition the latching hinge  100  back into the open state. This assumes that the preload from the spring-loaded tensioning device  114  has not yet been transferred to the latch mechanism—if this has occurred, then the contact surface  112  and the latch portion  110  will be drawn into compressive contact by the transferred pre-load. 
         [0058]    Also visible in greater detail in  FIG. 3  is the lever arm component  116 , which, in conjunction with the release mechanism  136 , may provide a trigger mechanism  118  that may be transitioned between an untriggered state and a triggered state. In the untriggered state, the trigger mechanism  118  may restrain the lever arm component  116 , whereas in the triggered state, the trigger mechanism  118  may permit the lever arm component  116  to move. The lever arm component  116  may include a fulcrum  126  about which the lever arm component  116  is configured to rotate. The fulcrum  126 , in this case, is provided by a rounded tip on the lever arm component  116  that rests in a V-shaped trough having a matching rounded bottom; a screw that passes through a hole in the lever arm component  116  prevents the lever arm component  116  from falling out of the trough if there is no load applied to the lever arm component  116  that pushes the lever arm component  116  into the trough. As can be seen, the lever arm component  116  is a third-class lever, although other implementations may utilize other classes of lever for the lever arm component  116 . 
         [0059]    In  FIG. 1 , the spring-loaded tensioning device  114  has been compressed into a first compressed state that causes the spring to apply a first compressive load to the latch hook  106  via the plunger  130  at compressive contact  146 . When the spring-loaded tensioning device  114  is released, it may enter a second compressed state and apply a second compressive load to the latch hook  106  that is lower in magnitude than the first compressive load. This, in turn causes a moment to be developed in the latch hook  106  around the first pivot  122 —the moment arm, in this case, is the distance D shown in  FIG. 1 . The latch hook  106  is restrained from rotating about the first pivot  122  by a countervailing torque developed through contact of the latch hook  106  with the lever arm component  116  at a first contact zone  138 . In this case, the lever arm component  116  applies a resisting force to the latch hook  106  via the first contact zone  138  that acts across the moment arm C; in this particular example, the resisting force will be less than the first compressive load since the moment arm C is greater than the moment arm D. 
         [0060]    The force applied to the first contact zone  138  by the latch hook  106  is, in turn, transmitted through the lever arm component  116  to the fulcrum  126 . As can be seen, the direction along which this force is applied, i.e., the peak magnitude vector of the force, is offset from the fulcrum by a distance A, causing a moment to be developed in the lever arm component  116  about the fulcrum  126 . This moment causes the lever arm component  116  to attempt to rotate towards the latch hook  106 , but the lever arm component  116  is prevented from doing so by a countervailing moment generated by a resistive force  150 , which has a peak magnitude vector that is offset by a distance B from the fulcrum  126 , applied to the moment arm component at a second contact zone  140 , which is formed between the lever arm component  116  and the release mechanism  136 . The distance A may, in some implementations, be at least an order of magnitude less than the distance B. 
         [0061]      FIG. 4  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state approximately halfway between the hinge-open state and a hinge-closed state. As can be seen, the positions of the components housed in each of the first member  102  and the second member  104  relative to those respective components has not changed from the positions shown in  FIG. 1 , although the second member  104  is rotating, and has rotated approximately 90°, about the hinge pivot  120  with respect to the first member  102 . It is to be understood that while the hinge-open state discussed herein has been shown as a state wherein the hinge in question is open to an angle of 180°, the hinge-open state may also correspond to a variety of other states, e.g., such as a state where the hinge must move through only 30°, 60°, 90°, 120°, 150°, or various other angles in order to reach the hinge-closed state. Broadly speaking, the hinge-open state may be any state in which the latch hook and the latch portion of the latch link are not latched together, although the normal hinge-open state for a latching hinge will typically be at angles such as 90° or 180° of angular separate between the first member  102  and the second member  104 . 
         [0062]      FIG. 5  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state of transition from the hinge-open state to the hinge-closed state where a latch portion of a latch link has contacted a portion of the latch hook. As can be seen, the first member  102   1  has rotated about the hinge pivot  120  with respect to the second member  104   1  such that the latch portion  110  of the latch link  108  has contacted a sloped surface  164  of the latch hook  106 . As the first member  102   1  continues to rotate about the hinge pivot  120 ; such continued movement is indicated by the white arrow, the sloped surface  164  will cause the latch portion  110  and the latch link  108  to rotate about the latch link pivot  124  and move in the direction shown by the grey arrow. 
         [0063]      FIG. 6  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state of transition from the hinge-open state to the hinge-closed state where the latch portion of the latch link has been deflected due to the portion of the latch hook. As can be seen in  FIG. 6 , the latch portion  110  and the latch link  108  have rotated about the latch link pivot  124 ; the latch portion  110  is held against the latch hook  106  by the latch link bias spring  132 , which acts to urge the latch link  108  back into its previous position. 
         [0064]      FIG. 7  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in a state of transition from the hinge-open state to the hinge-closed state where the latch link and the latch hook have latched together. As can be seen in  FIG. 7 , the latch link  108  has been forced back into to its original position with respect to the first member  102  by the latch link bias spring  132 , causing the latch portion  110  to move into a position proximate to the contact surface  112 . The contact surface  112 , in this arrangement, faces the latch portion  110 . At this point, the latching hinge  100  is considered latched since any attempt to return the first member  102  and the second member  104  to the open state will cause the latch portion  110  of the latch link  108  to be drawn into contact with the contact surface  112  of the latch hook  106 . Thus, while some small amount of clearance may exist between the latch portion  110  and the contact surface  112 , as shown in  FIG. 7 , this clearance may only permit a small amount of rotational movement, e.g., ˜1°-2°, between the first member  102  and the second member  104  before the latch portion  110  contacts the contact surface  112  and causes the rotation to stop. 
         [0065]      FIG. 9  depicts a side section view of the example latching hinge of  FIGS. 1 and 2  in the hinge-closed state. In  FIG. 9 , a number of components have moved in rapid succession or simultaneously. First, as the first member  102  rotated into the closed state with respect to the second member  104 , the trigger  144  engaged the release mechanism  136  and caused it to release the portion of the lever arm component  116  that was bearing on the second contact zone  140 . In other words, the trigger mechanism  118  transitioned from the untriggered state to the triggered state. Once released, the moment on the lever arm component about the fulcrum  126  caused by the application of force by the latch hook  106  to the first contact zone  138  causes the lever arm component  116  to pivot towards the latch hook  106  about the fulcrum  126 . In doing so, the portion of the lever arm component  1116  that provided the first contact zone  138  is moved into a position where it no longer resists movement of the latch hook  106 , at least for some amount of rotation of the latch hook  106  about the first pivot  122 . Once the lever arm component  116  has moved and no longer restrains the latch hook  106 , the latch hook  106  rotates about the first pivot  122 , allowing the spring-loaded tensioning device  114  to transition into the second compressed state that applies a second compressive load to the latch hook  106  and that causes the contact surface  112  to be drawn into the latch portion  110 . The latch hook  106  thus acts as a lever arm that transfers the second compressive load from the spring-loaded tensioning device to the latch link  108 , thus causing the latch link  108  to pull features on the first member  102 , e.g., concave prismatic surfaces  158  and concave conical surface  156 , into compressive contact with features on the second member  104 , e.g., convex prismatic surfaces  158 ′ and convex conical surface  156 ′. Put another way, the torque about the first pivot  122  by the application of the second compressive load to the latch hook  106  is applied to the latch portion  112  across a moment arm of distance E. 
         [0066]    As discussed above, the spring-loaded tensioning device may be provided using a stack of Belleville washers or other spring-type devices, e.g., coil springs.  FIGS. 8A and 8B  depict section views of an example spring-loaded tensioning device using Belleville washers in two different states of compression. As can be seen, the spring loaded tensioning device shown has a series of Belleville washers  828  stacked end-to-end along the length of a plunger  830 , and are compressed between the end of the plunger  830  and the shoulder of a base  842 . In  FIG. 8A , the washer stack is compressed to the limit of compressibility, i.e., the Belleville washers, which are normally conical, have been squashed flat. In  FIG. 8B , the washer stack has decompressed somewhat and caused the plunger  830  to extend slightly. As can be seen, there is now an angular gap that has appeared in between each pair of Belleville washers  828 . 
         [0067]    Many of the components of the latching hinge may be made from any of a variety of materials, including aluminum alloys, steel alloys, magnesium alloys, titanium alloys, or other metals or alloys. In some implementations, some of the components may be made from non-metallic materials such as plastics or composites. In the particular implementation shown in  FIGS. 1 through 9 , the first member  102  and the second member  104  were made from an aluminum alloy, whereas most of the other components discussed above were made from one or more different steel alloy. 
         [0068]    Various aspects of the example shown in  FIGS. 1 through 9  are discussed in greater detail below, although it is to be understood that these characteristics are subject to a wide degree of variation depending on a particular implementation of the concepts described herein. The hinge depicted in  FIGS. 1 through 9  is sized to accommodate equipment booms approximately 6″ in diameter, and the Belleville washer stack is compressed to a first compressive load of approximately 1500±200 pounds-force when the spring-loaded tensioning device  114  is in the first compressed state. Due to the different sizes of moment arm used in the latch hook  106  and the lever arm mechanism  116 , the amount of force that needs to be applied to the lever arm component  116  via the second contact zone  140  is approximately 10±1 pounds-force (compared to the ˜1500 pounds-force that the lever arm mechanism restrains). 
         [0069]    The latch portion  110  and the latch hook  106  latch together after the first member  102  and the second member  104  have rotated such that only about 2° of further relative rotation remains before the first member  102  and the second member  104  are in the hinge-closed state. The trigger  144  is designed to engage the release mechanism  136  and cause the release mechanism  136  to release the lever arm component  116  at some point between 2° and 0° of remaining closure angle. Once the spring-loaded tensioning device  114  has been released, it may extend the plunger  130  and enter the second compressed state, where it may apply a load of approximately 700 to 800 pounds-force to the latch hook  106 . This 700 to 800 pounds-force load is then rotationally coupled about the first pivot  122  and applied to the latch portion  110  of the latch link  108 ; due to the fact that the moment arms to the first pivot  122  differ in length between these two force applications, the latch portion  110  may experience a corresponding 810±100 pounds-force of load due to the application of 700 to 800 pounds-force of load to the latch hook  106  by the spring-loaded tensioning device  114 . Thus, as is clearly seen in this particular example, nearly a half-ton of preload may be transferred to the latch mechanism within one or two degrees of the latch mechanism latching, resulting in a latching hinge that is capable of withstanding—without any gaps forming between the first member and the second member—significant bending loads, e.g., greater than 1500 inch-pounds, that are applied via a connected equipment boom. Moreover, if the hinge pivot is constructed such that there are radial clearances within the hinge pivot and such that the rotational bearing surfaces of the hinge pivot do not contact one another due to forces exerted on the first and second members by the preload mechanism when the latching hinge is in the hinge-closed state, then none of this preload will be applied to the rotational components of the pivot hinge but may instead all be transferred directly from the first member to the second member. 
         [0070]    While the above-discussed example provides a solid understanding of the concepts towards which this disclosure is directed, the concepts discussed herein are not limited to the above-discussed variant alone. Various other configurations of such latching hinges may implement similar concepts. A discussion of some of these alternative implementations follows. 
         [0071]      FIG. 13  depicts a simplified diagram of a latching hinge with a spring-loaded tensioning device similar to the example shown in  FIGS. 2 through 12 . In  FIG. 13 , a first member  1302  and a second member  1304  are rotatably coupled by a hinge pivot  1320  and contact each other at linear alignment features  1358  and a radial alignment feature  1356  when in the hinge-closed state. A latch hook  1306  that may pivot about a first pivot  1322 , located in the second member  1304 , is acted on by a spring-loaded tensioning device  1314 ; the latch hook  1306  is prevented from rotating by a lever arm component  1316 , which is configured to rotate about a fulcrum  1326  but is restrained from doing so by a release mechanism (not pictured, but similar, for example, to the release mechanism shown in  FIGS. 1 through 1 ) acting on the opposite end of the lever arm component  1316  from the fulcrum  1326 . A latch link  1308 , which is rotatable about a latch link pivot  1324 , located in the first member  1302 , may have a latch portion  1310  that engages with the latch hook  1306 . The dotted outline shows how the latch link may rotate about the latch link pivot  1324  in order for the latch portion  1310  to clear the latch hook  1306  as the first member  1302  and the second member  1304  are transitioned to the hinge-closed state. This example functions, in essence, in the same manner as the example latching hinge  100  discussed above. 
         [0072]      FIG. 14  depicts a simplified diagram of an alternative mechanism for a latching hinge with a spring-loaded tensioning device. In  FIG. 14 , a first member  1402  and a second member  1404  are rotatably coupled by a hinge pivot  1420  and contact each other at linear alignment features  1458  and a radial alignment feature  1456  when in the hinge-closed state. A latch hook  1406  that may pivot about a first pivot  1422 , located in the second member  1404 , is acted on by a spring-loaded tensioning device  1414 ; the latch hook  1406  is prevented from rotating by a lever arm component  1416 , which is configured to rotate about a fulcrum  1426  but is restrained from doing so by a release mechanism (not pictured, but similar, for example, to the release mechanism shown in  FIGS. 1 through 1 ) acting on the opposite end of the lever arm component  1416  from the fulcrum  1426 . A latch link  1408 , which is rotatable about a latch link pivot  1424 , located in the first member  1402 , may have a latch portion  1410  that engages with the latch hook  1406 . The dotted outline shows how the latch link may rotate about the latch link pivot  1424  in order for the latch portion  1410  to clear the latch hook  1406  as the first member  1402  and the second member  1404  are transitioned to the hinge-closed state. This implementation is very similar to that shown in  FIG. 13 , with the chief difference being that the spring-loaded tensioning device  1414  has been moved to a different location and has been re-oriented such that it exerts force in a primarily vertical direction with respect to the orientation of the Figure and exerts such force on a different area of the latch hook  1406 . The latch hook  1406  is also somewhat altered from the latch hook  1406  to accommodate the new spring-loaded tensioning device  1414  location. In one sense, the spring-loaded tensioning device  1314  of  FIG. 13  may be viewed as exerting force along a spring extension axis that is generally perpendicular to the direction along which the tensile load is induced whereas the spring-loaded tensioning device  1414  of  FIG. 14  may be viewed as exerting force along a spring extension axis that is generally aligned with the direction along which the tensile load is induced. Of course, other implementations may feature a spring extension axis that extends along other directions, e.g., a direction oblique to the tensile load direction. 
         [0073]      FIG. 15  depicts a simplified diagram of another alternative mechanism for a latching hinge with a spring-loaded tensioning device. In  FIG. 15 , a first member  1502  and a second member  1504  are rotatably coupled by a hinge pivot  1520  and contact each other at linear alignment features  1558  and a radial alignment feature  1556  when in the hinge-closed state. A latch hook  1506  is provided that is fixed with respect to the second member  1504 . A latch link  1508 , located in the first member  1502 , may be supported by a crank arm  1570  that may be configured to rotate about a first pivot  1522 ; the latch link  1508  may be connected to the crank arm  1570  such that it may rotate about a latch link pivot  1524  with respect to the crank arm  1570 . The crank arm  1570  may be restrained from rotating about the first pivot  1522  by a lever arm component  1516 , which is configured to rotate about a fulcrum  1526  but is restrained from doing so by a release mechanism (not pictured, but similar, for example, to the release mechanism shown in  FIGS. 1 through 1 ) acting on the opposite end of the lever arm component  1516  from the fulcrum  1526 . The latch link  1508  may have a latch portion  1510  that engages with the latch hook  1506 . The dotted outline shows how the latch link may rotate about the latch link pivot  1524  in order for the latch portion  1510  to clear the latch hook  1506  as the first member  1502  and the second member  1504  are transitioned to the hinge-closed state. When the lever arm component  1516  is released by the release mechanism, the lever arm component  1516  may allow the crank arm  1570  to rotate about the first pivot  1522  due to force exerted on the crank arm  1570  by a spring-loaded tensioning device  1514 . This may cause the latch link pivot  1524 , and thus the latch link  1508 , to be drawn away from the second member  1504 , which, in turn, causes the latch hook  1506  to pull the second member  1504  and the first member  1502  into contact with one another, e.g., via the radial alignment feature  1556  and the linear alignment features  1558 . 
         [0074]      FIG. 16  depicts a simplified diagram of yet another alternative mechanism for a latching hinge with a spring-loaded tensioning device. In  FIG. 16 , a first member  1602  and a second member  1604  are rotatably coupled by a hinge pivot  1620  and contact each other at linear alignment features  1658  and a radial alignment feature  1656  when in the hinge-closed state. A latch hook  1606  is provided that is rotatably coupled to the second member  1604  via a latch pivot  1672 . A latch link  1608  may be provided that is part of a link arm  1674  that may be configured to rotate about a first pivot  1622 , which is located in the first member  1602 ; the latch link  1608  may remain motionless with respect to the first member  1602  until spring-loaded tensioning device  1614  is released. The latch hook  1606  may rotate, as indicated by the dotted outline, so as to allow the latch hook  1606  to engage with a latch portion  1610  of the latch link  1608 , deflect out of the way of the latch portion  1610 , and then snap into its original position so that the latch portion  1610  and the latch hook  1606  latch together. The link arm  1674  may be restrained from rotating about the first pivot  1622  by a lever arm component  1616 , which is configured to rotate about a fulcrum  1626  but is restrained from doing so by a release mechanism (not pictured, but similar, for example, to the release mechanism shown in  FIGS. 1 through 1 ) acting on the opposite end of the lever arm component  1616  from the fulcrum  1626 . When the lever arm component  1616  is released by the release mechanism, the lever arm component  1616  may allow the link arm  1674  to rotate about the first pivot  1622  due to force exerted on the link arm  1674  by a spring-loaded tensioning device  1614 . This may cause the latch link  1608  to be drawn away from the second member  1604  such that the latch portion  1610  contacts the latch hook  1606  and draws the latch hook  1606  towards the first member  1602 , which, in turn, causes the second member  1604  and the first member  1602  to be drawn into contact with one another, e.g., via the radial alignment feature  1656  and the linear alignment features  1658 . 
         [0075]    It is also to be understood that various types of release mechanism and/or triggers may be used in a latching hinge as discussed herein. Two implementations of such a mechanism are discussed below, but it is to be understood that other implementations may be used as well—in general, the release mechanism and trigger may be any device or combination of devices that can provide a restraining force, which may be a very small amount of force, e.g., more than two orders of magnitude less, as compared to the amount of force stored in the spring-loaded tensioning device, to the lever arm component and then release the restraining force after the latching hinge has latched shut. 
         [0076]      FIG. 17  depicts a diagram of a release mechanism in an unreleased state. The release mechanism  1736  may be provided by two opposing, thin, spring arms that each have a hole or detent in them. The lever arm component  1716  may have corresponding protrusions that may loosely fit within the holes such that the arms of the release mechanism  1736  restrain the lever arm component  1716  from moving in an “upwards” direction with respect to the orientation in the drawing. When a trigger  1744  approaches the release mechanism  1736 , the trigger may force the arms of the release mechanism  1736  apart as it engages the release mechanism  1736 , as shown in  FIG. 18 . Once the arms of the release mechanism  1736  are far enough apart, the protrusions on the lever arm component  1716  no longer engage with the holes in the arms, and the lever arm component  1716  is released. In  FIGS. 17 and 18 , the trigger  1744  and the lever arm component  1716  are located such that they do not collide with each other, e.g., the trigger  1744  may be “in front” of the lever arm component  1716  in the view shown. 
         [0077]      FIG. 19  depicts a diagram of a release mechanism in an unreleased state. The release mechanism  1936  may be provided by two opposing, thin arms that both have a jog in them that forms a ledge that the lever arm component  1916  may push against such that the arms of the release mechanism  1936  restrain the lever arm component  1916  from moving in an “upwards” direction with respect to the orientation in the drawing; the ledge may act as another form of “detent,” similar to the holes/detents of  FIG. 17 . When a trigger  1944  approaches the release mechanism  1936 , the trigger may force the arms of the release mechanism  1936  apart as it engages the release mechanism  1936 , as shown in  FIG. 20 . Once the arms of the release mechanism  1936  are far enough apart, the jogs/ledges on the arms of the release mechanism  1936  are no longer in contact with the lever arm component  1916  and allow the lever arm component  1916  to be released. In  FIGS. 19 and 20 , the trigger  1944  and the lever arm component  1916  are located such that they do not collide with each other, e.g., the trigger  1944  may be “in front” of the lever arm component  1916  in the view shown. 
         [0078]    As is apparent from the above discussion, there are a variety of different ways to implement the concepts discussed herein. The illustrated implementations represent only some of the myriad ways in which the concept discussed herein may be implemented, and this disclosure is not intended to be limited to only the pictured implementations. It is to be understood that other implementations that utilize a pre-load transfer mechanism that shifts a pre-compressed spring load from one load path to another in a latching hinge after the latching hinge has latched shut and by using various lever arms are also within the scope of this disclosure. 
         [0079]    The latching hinge discussed herein may be used in spacecraft designs to provide a mechanism by which deployable equipment booms may be attached to a spacecraft body such that the deployable equipment booms may be rotated from a stowed configuration into a deployed configuration. In some implementations, multiple latching hinges may be used at the joints of a multi-segment equipment boom, whereas in other implementations, latching hinges may be used to join a single equipment boom to another structure, e.g., the spacecraft body. 
         [0080]      FIG. 21  depicts a schematic of a spacecraft with an extensible equipment boom.  FIG. 22  depicts a schematic of the spacecraft of  FIG. 21  with the extensible equipment boom in a deployed state. As can be seen, spacecraft  2166  features an equipment boom  2168  that is connected to the spacecraft  2166  by a latching hinge  2100 , which may be similar to the latching hinges discussed herein. The latching hinge  2100  may, once the equipment boom  2168  is released, cause the equipment boom  2168  to swing away from the spacecraft  2166  into a deployed configuration, as shown in  FIG. 22 . The latching hinge  2100  may latch into position and then transfer the spring preload from the spring-loaded tensioning device into the latch mechanism, thereby taking up any slop in the rotational joint and also inducing a tensile preload across the hinge. 
         [0081]    Although several implementations of this invention have been described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope of spirit of the invention as defined in the appended claims.

Summary:
Latching or locking deployment hinges are provided that include a latch mechanism, a spring-loaded tensioning device, and a trigger mechanism. The trigger mechanism and the spring-loaded tensioning device are configured to transfer the compressed spring load in the spring-loaded tensioning device to the latch mechanism once the hinge has closed sufficiently far enough to latch together, thus inducing a pre-load through the latch mechanism that eliminates gapping in the hinge interface. The hinges may be sprung or actuated using a powered drive mechanism.