Patent Description:
Aircraft passenger compartments are pressurized in order to maintain comfortable oxygen levels for passengers and crew when cruising at high altitudes where ambient pressure is low and the air is thin. Adjacent compartments, such as a crown area or a cargo area, are divided from the passenger compartment by aircraft structure, such as stowage bins, ceilings, or floors. In the event of a decompression of a pressurized area, a pressure differential larger than desired could develop between the adjacent compartments. Aircraft may be equipped with closure panels that automatically open under a pressure differential to reduce the pressure differential. For example, latch assemblies are sometimes used that release a panel under a predetermined pressure differential on opposite sides of the panel.

<CIT>, in accordance with its abstract, states an apparatus, system and method including a latching device for displaceably retaining a panel relative to a frame. The latching device includes at least a bolt which is carried on the latching device and is operatively associated with the panel to prevent disengagement of the panel. The latching device includes at least one pressure responsive device operatively coupled to the bolt to retain the bolt in a desired position and release the bolt when a predetermined pressure differential occurs relative to two, generally opposite, sides of the panel or when a pressure decrease occurs on one side of the panel.

There is disclosed herein a latch assembly for a decompression panel in an aircraft, the latch assembly comprising a base and a swing arm. The swing arm is hinged to the base and is pivotable relative to the base between a latched position and an unlatched position. A load pin is fixed to the swing arm. A spring is secured to the base and is positioned to exert a spring force against the swing arm when the swing arm pivots from the latched position to the unlatched position. A bracket is securable to the decompression panel and defines a slot having an open end. The bracket is configured to retain the load pin in the slot when the swing arm is in the latched position. The load pin is movable in the slot under relative motion of the bracket and the base with the swing arm in the latched position, and the load pin exits the open end of the slot when the swing arm pivots from the latched position to the unlatched position under a force of the bracket on the load pin due to a pressure differential on the decompression panel. The force of the bracket on the load pin creates a moment on the swing arm that overcomes the spring force.

The swing arm may be pivotable relative to the base about a hinge axis between a latched position and an unlatched position. The load pin may have a pin axis a fixed distance from the hinge axis.

By securing the load pin to a moving part of the latch assembly (e.g., the swing arm) and configuring the swing arm and the bracket to function as a slip joint relative motion between the panel and aircraft structure to which the base is secured, such as may result from normal air turbulence, does not cause a variation in the magnitude of the force necessary to trigger the latch assembly. Such relative motion may be referred to as non-triggering relative motion. For example, a moment arm of the load pin from the hinge axis to the pin axis remains constant despite any such relative motion.

In some examples, the spring may be a beam spring having a fixed end and a supported end that floats on a support rod fixed to the base. The spring deflects between the fixed end and the supported end when the swing arm pivots from the latched position to the unlatched position. The spring may be a flat spring, such as a flat steel spring. The simplicity of a flat steel spring enables a highly accurate spring force determined by the thickness of the spring, and not dependent upon the geometry of bends or other features that may relax and cause a change in spring force over time. Moreover, as a flat spring may be symmetrical, it may be installed with either side facing the swing arm, simplifying installation.

Additionally, a shim may be disposed between the base and the spring. The shim may be used to adjust the spring force exerted by the spring on the swing arm. A sum of a thickness of the shim and a thickness of the spring affect the spring force of the spring acting against the swing arm when the swing arm moves from the latched position to the unlatched position.

A plate may be disposed over the spring nearer to the fixed end of the spring than the supported end of the spring. The plate is securable to the base with the spring sandwiched between the base and the plate. The plate helps to evenly distribute a securing force at the fixed end of the spring.

In some examples, the spring may be steel, and a coating may be disposed on the spring. The swing arm may contact the coating when pivoting from the unlatched position to the latched position. The coating lessens wear that could otherwise occur due to rubbing of the swing arm against the spring when in the latched position as a result of the relative motion of the components during aircraft travel. For similar reasons, a sleeve may be disposed around the load pin such that the sleeve, rather than the load pin, interfaces with the bracket in the slot.

Still further, to prevent rattling and wear due to the non-triggering relative motion, the spring may exert a preload on the swing arm when the swing arm is in the latched position and/or may exert a preload on the swing arm when the swing arm is in the unlatched position.

In some examples, the swing arm includes a cam having a profile configured to deflect the spring when the swing arm pivots from the latched position to the unlatched position. The profile of the cam may be configured such that a maximum deflection of the spring is between the latched position and the unlatched position. The cam profile thus helps to maintain the swing arm in the latched position until the bracket exerts at least a force of the predetermined magnitude acts on the load pin.

Additionally, the base may include a support that prohibits pivoting of the swing arm from the latched position in a direction away from the unlatched position. Stated differently, the support acts as a stop that blocks the swing arm from pivoting beyond the latched position. A compressible pad may be disposed on the support and may interface with the swing arm when the swing arm is in the latched position, dampening any rattle between the parts. Similarly, the base may include a support prohibiting pivoting of the swing arm from the unlatched position in a direction away from the latched position, and a compressible pad may be disposed on the support and may interface with the swing arm when the swing arm is in the unlatched position. This support acts as a stop that blocks the swing arm from pivoting beyond the unlatched position.

Also disclosed herein is aircraft comprising a fuselage, a first structure within the fuselage, and a second structure within the fuselage and spaced apart from the first structure, the fuselage, the first structure, and the second structure defining a first space and a second space, and an aircraft decompression system comprising: a decompression panel pivotably secured to the first structure and configured to at least partially span an opening between the first structure and the second structure in a closed position to at least partially separate the first space from the second space; and the latch assembly described above, wherein: the base is fixed to the second structure; the pressure differential on the decompression panel is due to a positive pressure differential between the first space and the second space; and the decompression panel pivots away from the opening into the second space.

In some examples of the aircraft decompression system, the first structure may be an outboard bin, the second structure may be an inboard bin, the first space may be a passenger cabin, the second space may be a crown space, and the decompression panel may be a ceiling panel. In some examples, unlatching of the latch assembly and the associated pivoting of the ceiling panel to the open position vents the passenger cabin into the crown space through the opening to reduce the difference between the pressures in the passenger cabin and the crown space.

There is disclosed herein a method of installing a decompression latch assembly in an aircraft. The aircraft has a fuselage, a first structure, a second structure, and a decompression panel within the fuselage. The fuselage, the first structure, and the second structure at least partially define a first space and a second space within the fuselage. The decompression panel at least partially spans an opening between the first structure and the second structure in a closed position of the decompression panel to at least partially separate the first space from the second space. The method includes securing a bracket of the decompression latch assembly to the decompression panel. The bracket defines a slot with an open end opening toward the second structure. The method includes fixing a base of the decompression latch assembly to the second structure, and inserting a load pin into the open end of the slot. The load pin is fixed to a swing arm that is hinged to the base. The swing arm is pivotable relative to the base between a latched position and an unlatched position, the bracket retaining the load pin in the slot when the swing arm is in the latched position. The load pin is movable in the slot under relative motion of the bracket and the base with the swing arm in the latched position. The method also includes securing a spring to the base and positioning the spring to exert a spring force against the swing arm when the swing arm pivots from the latched position to the unlatched position; wherein the load pin exits the open end of the slot when the swing arm pivots from the latched position to the unlatched position under a force of the bracket on the load pin due to a pressure differential on the decompression panel, the force of the bracket on the load pin creating a moment on the swing arm that overcomes the spring force.

In some examples, the method may further include securing the decompression panel to the first structure with a fixed latch assembly such that the decompression panel is pivotably secured to the first structure and pivots relative to the first structure at the fixed latch assembly when the swing arm pivots from the latched position to the unlatched position.

Additionally, the method may include inserting a shim between the base and the spring of the decompression latch assembly to adjust a magnitude of the spring force exerted by the spring against the swing arm and a magnitude of the force of the bracket on the load pin at which the swing arm pivots.

The above features and advantages, and other features and advantages, of the present teachings are readily apparent from the following detailed description of some examples for carrying out the present teachings, as defined in the appended claims, when taken in connection with the accompanying drawings.

A latch assembly disclosed herein enables decompression of a space, such as an aircraft passenger cabin or other space, by unlatching in response to a pressure differential across the panel to allow the panel to open to vent the space. The design of the latch assembly accounts for normal relative motion between the panel and aircraft structure to which the latch assembly latches the panel so that the latch assembly will not be unnecessarily triggered by the relative motion. Additionally, the latch assembly is configured so that the relative motion does not affect the force at which the latch assembly is triggered to open.

Referring to the drawings, wherein like reference numbers refer to like components, <FIG> shows a decompression latch assembly <NUM> for an aircraft <NUM> having an aircraft decompression system <NUM>, shown in <FIG>. The decompression latch assembly <NUM> may be referred to as a decompression latch assembly, or a pressure relief latch assembly. The decompression latch assembly <NUM> has a latched state, shown in <FIG>, <FIG>, <FIG>, and an unlatched state, shown in phantom in <FIG> and shown in <FIG>.

With reference to <FIG>, the aircraft <NUM> has a first structure <NUM> and a second structure <NUM> spaced apart from the first structure <NUM> within a fuselage <NUM>. In some examples, including the example shown, the first structure <NUM> is an outboard bin, and the second structure <NUM> is a center bin. The fuselage <NUM>, the first structure <NUM>, and the second structure <NUM> of the aircraft <NUM> define and encloses a first space <NUM>, shown as a passenger cabin, and a second space <NUM>, shown as a crown space. The first space <NUM> may be referred to as a first compartment <NUM>, and the second space <NUM> may be referred to as a second compartment <NUM>. A portion of the fuselage <NUM> is shown in <FIG>, and it should be appreciated that the fuselage <NUM> surrounds the first space <NUM> and the second space <NUM> to isolate these and other compartments of the aircraft <NUM> from the surrounding atmosphere.

The aircraft decompression system <NUM> includes the decompression latch assembly <NUM>, as well as a decompression panel <NUM>, which in the example shown is a ceiling panel. The decompression panel <NUM>, the outboard bin <NUM>, the center bin <NUM>, and other aircraft structure separates the first space <NUM> from the second space <NUM>. It should be appreciated that the first and second structures <NUM>, <NUM> are not limited to bins, the decompression panel <NUM> is not limited to a ceiling panel, and the first and second spaces <NUM>, <NUM> are not limited to a passenger cabin and crown space. In other examples, the decompression panel <NUM> may be a panel of a wall or a floor (instead of a ceiling panel), for example, the first compartment could be the cockpit instead of the passenger cabin and/or the second compartment could be a cargo space, for example.

The decompression panel <NUM> is pivotably secured to the first structure <NUM> with a fixed latch assembly <NUM>. The fixed latch assembly <NUM> is referred to as fixed because it is configured so that the decompression panel <NUM> can pivot at the fixed latch assembly <NUM> relative to the first structure <NUM>, but remains fixed to the first structure <NUM> by the fixed latch assembly <NUM>. The fixed latch assembly <NUM> has a first latch portion 28A fixed to the first structure <NUM>, and a second latch portion 28B fixed to the decompression panel <NUM>. The second latch portion 28B is hinged to the first latch portion 28A so that it pivots relative to the first latch portion 28A with the decompression panel <NUM>. Only one fixed latch assembly <NUM> is visible in side view in <FIG>, but there may be more than one fixed latch assembly <NUM> spaced along the end of the decompression panel <NUM> closest to the fixed structure <NUM> and pivotably securing the decompression panel <NUM> to the first structure <NUM>.

The decompression latch assembly <NUM> has a bracket <NUM> fixed to the decompression panel <NUM> in the second space <NUM> at an end of the decompression panel <NUM> closest to the second structure <NUM>. Only one decompression latch assembly <NUM> is shown in the side view of <FIG> but, like the fixed latch assembly <NUM>, there may be two or more than two decompression latch assemblies <NUM> spaced along the end of the decompression panel <NUM> nearest the second structure <NUM>.

The decompression panel <NUM> spans an opening <NUM> between the first structure <NUM> and the second structure <NUM> when the decompression latch assembly <NUM> is in the latched position shown in <FIG> to at least partially separate the first space <NUM> from the second space <NUM> at the opening <NUM>. The edge of the opening <NUM> is indicated in <FIG>, and the opening <NUM> extends the width and length of the decompression panel <NUM> (e.g., from the fixed latch assembly <NUM> to the decompression latch assembly <NUM>). Accordingly, air pressure in the first space <NUM> acts on a first side <NUM> of the decompression panel <NUM> (the bottom side in <FIG>) and air pressure in the second space <NUM> acts on a second side <NUM> of the decompression panel <NUM> (the top side in <FIG>). The decompression panel <NUM> is said to at least partially span the opening <NUM> to at least partially separate the first space <NUM> from the second space <NUM> as it need only separate the spaces <NUM>, <NUM> sufficiently to maintain a pressure differential less than the predetermined pressure differential at which the decompression latch assembly <NUM> unlatches.

Air is pressurized in the first space <NUM> during flight to maintain comfort for passengers and crew in light of the thin air of the surrounding atmosphere at high altitudes. The second space <NUM> need not be pressurized to the pressure level of the first space in order for it to serve its purposes, which may include containing and routing electrical, pneumatic, and other aircraft systems. In order to help maintain the desired pressure level in the first space, the decompression latch assembly <NUM> is configured to remain in the latched state when the pressure differential on the decompression panel <NUM> due to the pressurized first space <NUM> is less than a predetermined magnitude.

As discussed herein, a spring <NUM> (best shown in <FIG> and <FIG>) is secured to the base <NUM> and is positioned to bias the swing arm <NUM> to the latched position shown in <FIG> and exert a spring force when the swing arm <NUM> pivots from the latched position to the unlatched position. However, in the event that a pressure differential between the first space <NUM> and the second space <NUM> increases such that a net force F acting on the first side <NUM> of the decompression panel <NUM> results in at least a predetermined force PF of the bracket <NUM> on a load pin <NUM> of the decompression latch assembly <NUM>, a moment is created on the swing arm <NUM> that will overcome the biasing force of the spring <NUM>. The decompression latch assembly <NUM> will unlatch, allowing the decompression panel <NUM> to pivot at the fixed latch assembly <NUM> away from the first space <NUM> in the direction of arrow A to an open position in which the decompression panel <NUM> is shown in phantom at position 26A, lifted into the second space <NUM>. Opening of the decompression panel <NUM> allows pressure in the first space <NUM> to vent through the opening <NUM> into the lower pressure second space <NUM> to reduce the pressure differential.

Referring again to <FIG>, in addition to the bracket <NUM>, the decompression latch assembly <NUM> includes a base <NUM> and the swing arm <NUM>. The swing arm <NUM> is hinged to the base <NUM> and is pivotable relative to the base <NUM> about a hinge axis <NUM> between the latched position and the unlatched position. The load pin <NUM> is fixed to the swing arm <NUM> and has a pin axis <NUM> a fixed distance <NUM> from the hinge axis <NUM>. The distance <NUM> may be referred to as the moment arm of the load pin <NUM>. A sleeve <NUM> may be disposed around the load pin such that the load pin <NUM> extends through the sleeve <NUM>.

The bracket <NUM> is securable to the decompression panel <NUM> such as by bolts or screws that may extend through fastener openings <NUM> in a flange <NUM> of the bracket <NUM> so that the bracket <NUM> extends proud from the decompression panel <NUM> in the second space <NUM>, as shown in <FIG>. The bracket <NUM> has two elongated bars <NUM>, <NUM> that are spaced apart from one another to define a slot <NUM> between the bars <NUM>, <NUM>. The bars <NUM>, <NUM> extend from a brace portion <NUM> of the bracket <NUM> outward toward the base <NUM> when the decompression latch assembly <NUM> is installed in the aircraft <NUM> as shown in <FIG>. The slot <NUM> has an open end <NUM> directed toward the base <NUM>.

As shown in <FIG>, the bracket <NUM> is configured to retain the load pin <NUM> in the slot <NUM> when the swing arm <NUM> is in the latched position. As shown in <FIG>, the decompression panel <NUM> is in the closed position when the swing arm <NUM> is in the latched position. The sleeve <NUM>, rather than the load pin <NUM>, interfaces with the bracket <NUM> in the slot <NUM>. In some examples, the bracket <NUM>, the base <NUM>, and the swing arm <NUM> may each be an aluminum alloy. The load pin <NUM> may be but is not limited to stainless steel. The sleeve <NUM> may be nylon and may have an internal diameter <NUM> (see <FIG>) that fits to the external diameter <NUM> (see <FIG>) of the load pin <NUM> so that the sleeve <NUM> surrounds the load pin <NUM>. Using a sleeve <NUM>, such as a nylon sleeve, reduces friction with the bars <NUM>, <NUM> in comparison to the stainless steel load pin <NUM>, reducing wear with relative motion and easing exit of the load pin <NUM> from the slot <NUM> during unlatching.

Referring to <FIG>, each of the bars <NUM>, <NUM> has a straight portion 58A, 60A, respectively, and a curved end 58B, 60B, respectively. The curved ends 58B, 60B diverge apart from one another. The slot <NUM> has a length <NUM> along the straight portions 58A, 60A that is sufficient to allow expected relative motion in a direction along the slot <NUM> that may occur between the decompression panel <NUM> and the second structure <NUM> during flight so that the load pin <NUM> remains in the slot <NUM> and the swing arm <NUM> remains in the latched position until a triggering predetermined force PF on the load pin <NUM> causes unlatching.

The load pin <NUM> will exit the open end <NUM> of the slot <NUM> during unlatching. The load pin <NUM> and sleeve <NUM> will move along a convex surface <NUM> at the curved end 60B of the bar <NUM> when exiting the open end <NUM>, allowing the bar <NUM> to continue transferring the force PF to the swing arm <NUM> as the swing arm <NUM> pivots toward the unlatched position, ensuring that the swing arm <NUM> overcomes the biasing force of the spring <NUM> and is pushed by the bracket <NUM> to the unlatched position.

Accordingly, the swing arm <NUM> and the bracket <NUM> function as a slip joint due to the ability of the load pin <NUM> to move within the slot <NUM> without exiting the slot <NUM> until a triggering predetermined force PF is applied by the bracket <NUM>. By securing the load pin <NUM> to a moving part of the decompression latch assembly <NUM> (e.g., the swing arm <NUM>) and configuring the swing arm <NUM> and the bracket <NUM> to function as a slip joint allowing relative motion between the decompression panel <NUM> and the second structure <NUM> to which the base <NUM> is secured, the magnitude of the predetermined force necessary to trigger the latch assembly <NUM> is not varied due to the relative motion as it would be if the load pin <NUM> were instead fixed to the bracket <NUM>, in which case the moment arm of the load pin <NUM> to the hinge axis <NUM> would vary with the relative motion. Instead, a moment arm (fixed distance <NUM>) of the load pin <NUM> from the hinge axis <NUM> to the pin axis <NUM> remains constant despite such relative motion.

Referring to <FIG>, the base <NUM> include includes a flange <NUM> with a plurality of fastener openings <NUM> through which fasteners extend to secure the base <NUM> to the second structure <NUM>. Fasteners <NUM> are shown in <FIG>. The base <NUM> includes outer supports <NUM> and inner supports <NUM> that extend outward from the flange <NUM>. The inner supports <NUM> are spaced apart from one another by a spacing <NUM> sufficient to allow a fixed end 35A of the spring <NUM> to be disposed on a surface <NUM> of the flange <NUM> at fastener openings <NUM> (see <FIG>). Each support <NUM>, <NUM> includes a hinge pin opening <NUM>, and the hinge pin openings <NUM> are aligned with one another and together define the hinge axis <NUM>.

The spring <NUM> is shown in <FIG> as a flat spring of uniform thickness T with a fixed end 35A and a supported end 35B. The spring <NUM> has openings <NUM> spaced to align with the openings <NUM> when secured to the base <NUM> of <FIG>. The fixed end 35A is referred to as fixed because it is secured to the base <NUM> as discussed herein and does not deflect when the swing arm <NUM> pivots. The supported end 35B floats on a support rod <NUM> that is fixed to the base <NUM>. The surface <NUM> of the flange <NUM> angles outward to create a recess <NUM> in the spacing <NUM> that gives the spring <NUM> room to bend between the fixed end 35A and the supported end 35B when moved by the swing arm <NUM>. The supported end 35B is referred to as floating because it rests on but is not fixed to the support rod <NUM> and slides against the support rod <NUM> as the spring <NUM> deflects (bends) to allow the swing arm <NUM> to move from the latched position to the unlatched position.

As shown, the support rod <NUM> may include an outer sleeve 39A that the supported end 35B contacts, and an inner pin 39B. Similar to sleeve <NUM> on the load pin <NUM>, the outer sleeve 39A may be nylon and may have an internal diameter that fits to the external diameter of the inner pin 39B so that the outer sleeve 39A surrounds the inner pin 39B. The inner pin 39B may extend through openings in the inner supports <NUM> and be secured to the supports via a screw <NUM> integral with or extending through the inner pin 39B and a lock nut <NUM>, for example. Using an outer sleeve 39A, such as a nylon sleeve, reduces friction with the supported end 35B in comparison to the inner pin 39B, which may be steel, for example, reducing wear.

A spring force of the spring <NUM> against the swing arm <NUM> is dependent upon the material of the spring <NUM> and the thickness T, which are selected to provide a spring stiffness that causes the spring <NUM> to deflect sufficiently to allow the swing arm <NUM> to unlatch when the predetermined force PF at which the aircraft decompression system <NUM> is designed to open the decompression panel <NUM> acts upon the load pin <NUM>.

Referring to <FIG>, the swing arm <NUM> includes two spaced knuckles <NUM> each of which defines a hinge pin opening <NUM> which aligns with the hinge pin openings <NUM> along the hinge axis <NUM>. As best shown in <FIG>, two hinge pins <NUM> are used to connect the swing arm <NUM> (only knuckles <NUM> shown in <FIG>) to the base <NUM>. Each hinge pin <NUM> extends through the openings <NUM> of one inner support <NUM> and one outer support <NUM>. The hinge pin opening <NUM> of one of the knuckles <NUM> is disposed between the pair of inner and outer supports <NUM>, <NUM>.

Clips <NUM>, referred to herein as C-clips <NUM>, fit within grooves <NUM> of the hinge pins <NUM> to retain the hinge pins <NUM> in the openings <NUM>, <NUM>. As used herein, a C-clip is a retaining ring with open ends that can be snapped into place in a pin, rod, or shaft, such as in the grooves <NUM> in hinge pins <NUM>, to permit rotation but to act as a barrier to prevent lateral movement of an object adjacent to the C-clip on the pin. One C-clip <NUM> is shown in <FIG> and one hinge pin <NUM> with grooves <NUM> is shown in <FIG>.

The hinge pins <NUM> may be but are not limited to stainless steel. Two hinge sleeves <NUM> may be used, each extending around the outer diameter of a respective hinge pin <NUM> between the grooves <NUM> of the hinge pin <NUM> so that the hinge sleeve <NUM> interfaces with the swing arm <NUM> at the openings <NUM> and with the supports <NUM>, <NUM> at the openings <NUM> to reduce friction and wear on the hinge pins <NUM>. A hinge sleeve <NUM> is also shown in <FIG>. The hinge sleeves <NUM> may be but are not limited to nylon.

The outer supports <NUM> include stops <NUM> that prohibit pivoting of the swing arm <NUM> from the latched position in a direction away from the unlatched position. Stated differently, each outer support <NUM> acts as a stop that blocks the swing arm <NUM> from pivoting beyond the latched position. A compressible pad <NUM> may be disposed on and adhered to the surface of the stop <NUM> and may interface with the swing arm <NUM> when the swing arm <NUM> is in the latched position, dampening any rattle between the swing arm <NUM> and the stop <NUM>. <FIG>, <FIG> best show the swing arm <NUM> interfacing with a compressible pad <NUM> with the stop <NUM> blocking further pivoting of the swing arm <NUM> in a direction away from the unlatched position. One compressible pad <NUM> is shown in <FIG>. The compressible pad <NUM> may be but are not limited to silicone.

Similarly, as shown in <FIG>, the inner supports <NUM> include stops <NUM> that prohibit pivoting of the swing arm <NUM> from the unlatched position in a direction away from the latched position. Each support <NUM> acts as a stop that blocks the swing arm <NUM> from pivoting beyond the unlatched position. A compressible pad <NUM> may be disposed on and adhered to the surface of the stop <NUM> and may interface with the swing arm <NUM> when the swing arm <NUM> is in the unlatched position, dampening any rattle between the swing arm <NUM> and the stop <NUM>. <FIG> best shows the swing arm <NUM> interfacing with a compressible pad <NUM> with the stop <NUM> blocking further pivoting of the swing arm <NUM> in a direction away from the unlatched position.

Referring to <FIG>, the swing arm <NUM> includes two arm portions 44A and 44B that are spaced apart from one another. Each arm portion 44A, 44B has an opening <NUM>. The openings <NUM> are aligned to define the pin axis <NUM>. As shown in <FIG>, the load pin <NUM> extends through the openings <NUM>. The openings <NUM> are sized to allow the load pin <NUM> but not the sleeve <NUM> to extend therethrough, as shown in <FIG> and <FIG>. Referring to <FIG>, the load pin <NUM> has circumferential grooves <NUM> like those of the hinge pins <NUM> to receive a C-clip <NUM> as shown in <FIG> and <FIG>, for example.

Referring again to <FIG>, the swing arm <NUM> includes a cam <NUM> disposed between the two spaced knuckles <NUM> and extending further than the knuckles <NUM> away from the ends of the arm portions 44A, 44B that support the load pin <NUM>. The cam <NUM> has a cam surface <NUM> with a profile <NUM> configured to deflect the spring <NUM> when the swing arm <NUM> pivots from the latched position to the unlatched position. The profile <NUM> of the cam <NUM> is configured such that a maximum deflection of the spring <NUM> is between the latched position and the unlatched position. For example, referring to <FIG>, the cam surface <NUM> includes a first surface portion 102A, a second surface portion 102B, and a tip portion 102C between the first and second surface portions 102A, 102B. When in the latched position, the first surface portion 102A rests against the spring <NUM> as shown in <FIG>. The cam <NUM> is configured so that the spring <NUM> is slightly deflected (e.g., the spring <NUM> is pushed slightly toward the base <NUM> between the support end 35B and the fixed end 35A) to provide a preload on the cam <NUM> to help maintain the swing arm <NUM> in the latched position and to prevent rattling and wear of the cam <NUM> against the spring <NUM> due to the non-triggering relative motion described herein.

When in the unlatched position, the second surface portion 102B rests against the spring <NUM>, as shown in <FIG>. The cam <NUM> is configured so that the spring <NUM> is slightly deflected (e.g., the spring <NUM> is pushed slightly toward the base <NUM> between the support end 35B and the fixed end 35A) to provide a preload on the cam <NUM> to help maintain the swing arm <NUM> in the unlatched position to prevent rattling and wear due to the non-triggering relative motion.

To move the swing arm <NUM> from the latched position to the unlatched position, and vice versa, the tip portion 102C of the cam <NUM> passes over and against the spring <NUM> (e.g., against the coating <NUM> thereon). Because the tip portion 102C is the furthest extent of the cam <NUM> in a direction opposite to that of the direction from the hinge axis <NUM> to the pin axis <NUM> (e.g., opposite to the moment arm), the spring <NUM> will experience maximum deflection due to the swing arm <NUM> at an intermediate position between the latched position and the unlatched position, as shown in <FIG>. The cam profile <NUM> is configured so that the predetermined force PF is that force which causes deflection of the spring <NUM> by an amount at which the tip portion 102C contacts the spring <NUM> (e.g., deflects the spring <NUM> to the intermediate position of <FIG>). The cam profile <NUM> thus helps to maintain the swing arm <NUM> in the latched position until at least a force of a magnitude of the predetermined force PF acts on the load pin <NUM>.

The cam profile <NUM> is not symmetrical in that the first surface portion 102A is slightly longer than the second surface portion 102B so that the tip portion 102C is slightly skewed in one direction. An asymmetrical marker <NUM> (see <FIG>) is provided on one or both of the arm portions 44A to indicate a direction in which the swing arm <NUM> should be oriented so that the first surface portion 102A interfaces with the spring <NUM> in the unlatched position. In some examples, including the example shown, the asymmetrical marker <NUM> is a triangle with an apex indicating an up direction in which the swing arm <NUM> should be oriented before inserting the hinge pins <NUM> through the openings <NUM>.

Referring to <FIG>, relative motion between the bracket <NUM> and the base <NUM> can occur in the horizontal direction X of <FIG> along the length <NUM> of the straight portions 58A, 60A without the load pin <NUM> exiting from the slot <NUM>. The load pin <NUM> may thus slide between a closed end <NUM> of the slot <NUM> and an inflection of the bars <NUM>, <NUM> at the end of the straight portion where the bars <NUM>, <NUM> begin to curve at curved ends 58B, 60B. Relative motion may also occur in the vertical direction Y of <FIG>, in any amount that results in a force on the load pin <NUM> by the bracket <NUM> less than the predetermined force PF, as the spring <NUM> will prevent the swing arm <NUM> from moving past the tip portion 102C of the cam profile <NUM> at such relatively low forces. Accordingly, a pressure differential between the compartments <NUM>, <NUM> less than the predetermined pressure differential on the decompression panel <NUM> will not unlatch the decompression latch assembly.

Referring to <FIG>, the spring <NUM> is shown as a beam spring having the fixed end 35A and the supported end 35B. The spring <NUM> is a flat steel spring in the example shown, but in other examples may be a different material and need not be flat. The simplicity of a flat steel spring enables a highly accurate spring force determined by the thickness T of the spring <NUM>, and not requiring bends or other features that may relax and cause a change in spring force over time. Although the spring <NUM> is depicted as a beam spring with a supported end 35B, in other examples, the spring <NUM> could instead be a cantilevered beam with a free end (not support rod <NUM>) for example. By configuring the spring <NUM> as a beam spring with a fixed end 35A and a supported end 35B with the supported end 35B floating on the rod <NUM> as described, the desired unlatching at the predetermined force PF may be easier accomplished than with a cantilever spring, for example. The thickness T may be reduced in comparison to a cantilever spring with a free end, for example.

Moreover, as a flat spring may be symmetrical, it may be installed with either side facing the cam <NUM>. In some examples, a coating <NUM> is disposed on the outer surface of the spring <NUM>, as indicated in <FIG>. The coating <NUM> lessens wear that could otherwise occur due to rubbing of the cam <NUM> of the swing arm <NUM> against the spring <NUM> when in the latched position as a result of the normal relative motion of the latch assembly components (e.g., bracket <NUM> and base <NUM>) during flight, as previously discussed. Because the spring <NUM> is symmetrical and may be installed with either side facing the cam <NUM>, both sides of the spring <NUM> are coated. The spring <NUM> may be a spring stainless steel finished with a zinc-nickel alloy plate, followed by a coat of primer and then the coating <NUM>, which may be but is not limited to polytetrafluoroethylene (PTFE) polyester.

Additionally, a shim <NUM> may be used, and is shown disposed between the base <NUM> and the spring <NUM>. The shim <NUM> is shown in <FIG> with fastener openings <NUM> to allow screws like screw <NUM> shown in <FIG> to extend through the shim <NUM> when fastening the shim <NUM> and the spring <NUM> to the base <NUM>. The shim <NUM> is used to adjust the spring force exerted by the spring <NUM> on the swing arm <NUM>. A sum of a thickness of the shim <NUM> and a thickness of the spring <NUM> affect the spring force of the spring <NUM> acting against the swing arm <NUM> when the swing arm moves from the latched position to the unlatched position. The shim <NUM> may be a machined aluminum alloy.

A plate <NUM>, referred to as a clamping plate <NUM>, is disposed over the spring <NUM> nearer to the fixed end 35A of the spring <NUM> than the supported end 35B of the spring <NUM>. The plate <NUM> is shown in <FIG> with fastener opening <NUM> that align with the openings <NUM> of the spring <NUM> and the openings <NUM> of the shim <NUM> so that the plate <NUM> is securable to the base <NUM> with the spring <NUM> sandwiched between the base <NUM> and the plate <NUM>. The plate <NUM> may be an aluminum alloy. The plate <NUM> helps to evenly distribute a securing force at the fixed end 35A of the spring <NUM>. Screws <NUM> shown in <FIG> and <FIG> extend through the aligned openings <NUM>, <NUM>, <NUM> and <NUM> are secured with lock nuts <NUM> (one shown in <FIG>) against washers <NUM> (also shown in <FIG>) to tighten the fixed end 35A in place on the base <NUM>. The spring <NUM> is of a length such that the supported end 35B moves along and stays in contact with the outer surface of the support rod <NUM> as the swing arm <NUM> moves from the latched position to the unlatched position and vice versa.

A method <NUM> of installing the decompression latch assembly in an aircraft is disclosed, and is described with respect to the decompression latch assembly <NUM> and the aircraft <NUM>. <FIG> is a flowchart illustrating the method <NUM>. In some examples, the method <NUM> may include step <NUM>, securing the decompression panel <NUM> to the first structure <NUM> (e.g., the outboard bin <NUM>) with a fixed latch assembly <NUM> such that the decompression panel <NUM> is pivotably secured to the first structure <NUM> and pivots relative to the first structure <NUM> at the fixed latch assembly <NUM>. Alternatively, the decompression panel <NUM> may already be secured to the first structure <NUM> with the fixed latched assembly <NUM> when the method <NUM> begins.

The method <NUM> includes step <NUM>, securing the bracket <NUM> of the latch assembly <NUM> to the decompression panel <NUM>. The bracket <NUM> defines a slot <NUM> with an open end <NUM> opening toward the second structure <NUM> (e.g., the center bin <NUM>). Stated differently, when securing the bracket <NUM> to the decompression panel <NUM>, the installer orients the open end <NUM> toward the second structure <NUM> instead of toward the first structure <NUM> (e.g., the outboard bin <NUM>).

The method <NUM> includes step <NUM>, fixing a base <NUM> of the latch assembly <NUM> to the second structure <NUM>. Step <NUM> may be completed either before or after completing step <NUM>. The method <NUM> further includes step <NUM>, inserting the load pin <NUM> into the open end <NUM> of the slot <NUM>. The load pin <NUM> is fixed to the swing arm <NUM> that is hinged to the base <NUM>. The load pin <NUM> may already be fixed to the swing arm <NUM> when inserted into the slot <NUM>, and the swing arm <NUM> may already be hinged to the base <NUM>. The swing arm <NUM> is pivotable relative to the base <NUM> between the latched position and the unlatched position, the bracket <NUM> retaining the load pin <NUM> in the slot <NUM> when the swing arm <NUM> is in the latched position. The load pin <NUM> is movable in the slot <NUM> under relative motion of the bracket <NUM> and the base <NUM> with the swing arm <NUM> in the latched position. The method <NUM> further includes securing a spring <NUM> to the base <NUM> and positioning the spring <NUM> to exert a spring force against the swing arm <NUM> when the swing arm <NUM> pivots from the latched position to the unlatched position; wherein the load pin <NUM> exits the open end <NUM> of the slot <NUM> when the swing arm <NUM> pivots from the latched position to the unlatched position under a force of the bracket <NUM> on the load pin <NUM> due to a pressure differential on the decompression panel <NUM>, the force of the bracket <NUM> on the load pin <NUM> creating a moment on the swing arm <NUM> that overcomes the spring force.

Additionally, the method <NUM> may include step <NUM>, inserting a shim <NUM> between the base <NUM> and a spring <NUM> of the latch assembly <NUM> to adjust a magnitude of a spring force exerted by the spring <NUM> against the swing arm <NUM> and a magnitude of the predetermined force PF applied to the load pin <NUM> at which the swing arm <NUM> pivots. For example, step <NUM> may be accomplished if it is determined that the spring force needs to be adjusted to achieve a desired predetermined force PF at which unlatching of the latch assembly <NUM> is triggered. Alternatively, a shim <NUM> may already be inserted as described when the method <NUM> begins, or there may be no shim <NUM> included in the latch assembly.

Accordingly, the decompression latch assembly <NUM> disclosed herein is able to respond to relative motion between components of the aircraft <NUM> caused by turbulence for example, without a variation in the force necessary to unlatch the decompression latch assembly <NUM>. The decompression latch assembly <NUM> opens at a predetermined pressure differential between two compartments in the aircraft <NUM> that results in a predetermined force PF on the load pin <NUM> by unlatching regardless of the relative position of the load pin <NUM> in the slot <NUM> of the bracket <NUM>, allowing the decompression panel <NUM> to pivot into the second compartment <NUM> to vent the first compartment <NUM>.

Claim 1:
A latch assembly (<NUM>) for a decompression panel (<NUM>) in an aircraft (<NUM>), the latch assembly comprising:
a base (<NUM>);
a swing arm (<NUM>) hinged to the base (<NUM>) and pivotable relative to the base (<NUM>) between a latched position and an unlatched position;
a load pin (<NUM>) fixed to the swing arm (<NUM>);
a spring (<NUM>) secured to the base (<NUM>) and positioned to exert a spring force against the swing arm (<NUM>) when the swing arm (<NUM>) pivots from the latched position to the unlatched position; and
a bracket (<NUM>) securable to the decompression panel (<NUM>), the bracket (<NUM>) defining a slot (<NUM>) having an open end (<NUM>), the bracket (<NUM>) configured to retain the load pin (<NUM>) in the slot (<NUM>) when the swing arm (<NUM>) is in the latched position, the load pin (<NUM>) movable in the slot (<NUM>) under relative motion of the bracket (<NUM>) and the base (<NUM>) with the swing arm (<NUM>) in the latched position, and the load pin (<NUM>) exiting the open end (<NUM>) of the slot (<NUM>) when the swing arm (<NUM>) pivots from the latched position to the unlatched position under a force of the bracket (<NUM>) on the load pin (<NUM>) due to a pressure differential on the decompression panel (<NUM>), the force of the bracket (<NUM>) on the load pin (<NUM>) creating a moment on the swing arm (<NUM>) that overcomes the spring force.