Actuator rate control with energy absorbing pressure relief system

An actuator includes a piston assembly movably disposed within an assembly housing having a fixedly supported end and an opposing end that receives a movable piston assembly. The piston assembly includes a piston rod and an attached piston head having a fixed orifice as well as an orifice with a check valve to create rate control of the assembly. Hydraulic fluid is caused to move through the axially movable piston head based on compressive and tensile loads imparted to the assembly. A plurality of pre-loaded springs are configured to selectively provide pressure relief in the event the orifices of the piston become clogged, wherein the plurality of pre-loaded springs, such as disc springs, further provide an energy absorbing function of the assembly based on loading conditions.

TECHNICAL FIELD

This application is generally directed to the field of actuator assemblies and more specifically to an actuator assembly that permits rate control, as well as an energy absorbing pressure relief. The actuator assembly can be used preferably in connection with an emergency door used on commercial aircraft.

BACKGROUND

Emergency doors as used in connection with commercial aircraft are movable between a closed or locked state and an opened state. Upon opening, the emergency door is typically moved outside the aircraft and away from the door opening but is still attached. Upon opening of the emergency door, an inflatable slide is deployed to enable passengers to leave the aircraft.

Actuators often used in connection with the opening of the emergency doors include a spring means to open the door from a closed to an opened position and a piston assembly having a piston rod and at least one piston head that is configured to move within a sealed cylinder containing a hydraulic fluid. The piston head includes at least one orifice that permits fluidic flow between defined chambers to produce a resisting force to control the opening rate of the door. A shock absorbing end stop is also incorporated to prevent a high load on the door assembly when the door reaches its fully open position.

BRIEF DESCRIPTION

According to one aspect, there is provided an actuator assembly comprising a cylindrical housing having opposing first and second ends and a hollow interior; a movable piston assembly disposed within the interior, the piston assembly including a piston head having a fixed orifice; and a check valve disposed in another orifice. The actuator assembly further comprises spring means disposed in relation to the piston head, the spring means being compressible to create energy storage at the end of the extension stroke.

In one version, a pressure relief valve is also provided in the event that fluid movement through the orifices of the piston head is disabled. The pressure relief valve is enabled by movement of the piston head against the spring means, such as, for example, a plurality of disc springs that are caused to move in the event the fixed orifice of the piston head is blocked and enabling fluid flow along a flat of the piston rod through a defined flow path from the high pressure side to the low pressure side of the piston head in the hydraulic chamber.

According to one embodiment, one connecting end of the assembly housing including the piston assembly is configured for attachment to an emergency door of an aircraft and an opposing end of the housing is configured for fixed attachment to an aircraft structure.

In at least one version, an accumulator piston is disposed in an end of the assembly housing opposite the piston assembly, in which the accumulator piston is biased by a coil spring. The herein described assembly further includes at least one pre-loaded coil spring attached onto the exterior of the assembly housing to provide the actuation force.

According to another aspect, there is provided an actuator assembly comprising an assembly housing having opposing first and second ends and a hollow interior. At least one coil spring is attached to the exterior of the assembly housing and a bearing member is fixedly attached within the interior of the assembly housing and sealingly engaged therewith. The actuator assembly further comprises a piston assembly made up of a piston rod and a piston head having a plurality of axial orifices. The piston assembly is movable through a sealed opening of the bearing member into a chamber filled with hydraulic fluid. A check valve is disposed in one of the axial orifices, the check valve preventing fluid flow through the orifice when fluid is moved in one axial direction. An accumulator piston biased by an accumulator spring is disposed at an opposite end of the assembly housing relative to the bearing member, and at least one spring is disposed adjacent to the piston head and pre-loaded in compression to enable energy storage of an applied load.

According to a preferred embodiment, a pressure relief valve is enabled by fluid pressure against the piston head when the orifices of the piston head are clogged. The pressure relief valve includes a flat disposed on the piston rod and at least one vent within the piston rod extending to the hydraulic fluid chamber wherein fluid pressure against the piston head causes deflection of the adjacent at least one spring, enabling the opening of the pressure relief valve.

The check valve is configured to close upon extension movement of the assembly, thereby creating rate control.

According to another aspect, there is provided an actuator assembly for an emergency door of a commercial aircraft, the assembly comprising a housing having a first end, an opposing second end and a hollow interior. Connecting end members are provided at the first and second ends of the cylindrical housing. A piston assembly includes a piston rod and a piston head, the piston assembly being movably attached to one of the connecting end members. An accumulator piston is biased by an accumulator spring, the accumulator piston and the piston head each being sealingly engaged within the hollow interior of the cylindrical housing and defining a fluidic chamber therebetween, wherein the piston head includes axial orifices extending therethrough, one of the orifices including a check valve. The actuator assembly further includes a bearing member disposed between the piston head that is sealingly engaged with the assembly housing and at least one spring member disposed adjacent the piston head. Movement of the piston assembly in a first direction causes fluidic flow through each of the orifices of the piston head and fluidic flow is prevented through the check valve when the piston assembly is moved in a second direction opposite to the first direction to create damping as the emergency door is moved to an extended position.

According to an exemplary embodiment, the at least one spring member is disposed in a pre-loaded condition and caused to deflect if the orifices of the piston head become occluded or blocked, thereby enabling a pressure relief valve. In at least one version, the pressure relief valve comprises a flat formed on the piston rod extending to a vent formed in the piston rod adjacent to the flat to permit the passage of fluid when fluid pressure causes the piston head to move against the at least one spring member. The at least one spring member can comprise, for example, a plurality of pre-loaded disc springs.

One of the ends of the assembly housing is attached to the movable door of the commercial aircraft and the opposing end is attached to a fixed portion of the aircraft structure.

According to yet another aspect, there is provided an emergency door system for a commercial aircraft comprising a door movable between an extended and a non-extended position and an actuator assembly. The actuator assembly comprises an actuator assembly that includes a cylindrical housing having opposing first and second ends and a hollow interior containing a hydraulic fluid, the first end being connected to the movable door and the second end being fixedly connected to the aircraft structure. A movable piston assembly is attached to the movable door and disposed within the hollow interior. The piston assembly includes a piston head having a fixed orifice and a check valve disposed in another orifice. At least one preloaded spring member is disposed in relation to the piston head, the at least one preloaded spring member being compressible to create energy storage at the end of the extension stroke.

According to a preferred embodiment, the system includes a pressure relief valve that is enabled when the orifices of the piston head are blocked and unable to move hydraulic fluid and in which the pressure relief valve is enabled when sufficient fluid pressure moves the piston head and causes deflection of the at least one preloaded spring member. The valve further includes a flow path formed in the piston rod by a flat formed in the piston rod and in which deflection of the at least one preloaded spring member and movement of the piston head enables fluid to flow from the high pressure side to the low pressure side of the piston head in the hydraulic chamber.

Advantageously, the actuator/rate control unit provides a consistent spring force over a wide temperature range to open the emergency door of an aircraft, provides speed control to control the opening rate of the door, and provides an energy absorber at the end of the extension stroke to decelerate the door at the fully open position and limit the loads on the door.

It is vital that the emergency door on the aircraft be caused to open for safety and related reasons. The combination energy absorber and pressure relief system in the actuator/rate control unit insures the door can be opened should the piston head orifice holes become plugged for any reason.

These and other features and advantages will be readily apparent from the following Detailed Description, which should be read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION

This description relates to exemplary embodiments of an actuator assembly, that can be used by way of example in connection with an aircraft emergency door. It will be readily understood, however, that the concepts discussed herein are applicable to other suitable applications and uses in the aircraft, as well as other fields. In addition and throughout this discussion, several terms such as “front”, “rear, “above”, “below”, “distal”, “proximal”, “inner”, “outer” and the like are used in order to provide a suitable frame of reference in regard to the accompanying drawings. These terms, however, are not intended to narrow the intended scope of the invention, unless clearly indicated otherwise.

With reference toFIGS. 1-3B, there is shown an actuator assembly100that is made in accordance with an embodiment of the invention. The actuator assembly100is defined by an assembly housing102made up of a cylindrical shock tube104, as well as an axial end108and a clevis sleeve134attached to opposing ends of the shock tube104. The assembly housing102is defined by a hollow interior105that is sized and configured to retain a plurality of components, as further discussed herein.

A pair of connecting end members117and119are attached to a piston rod140and an opposing end112of the assembly housing102, respectively. More specifically, the connecting end member117engages a sleeve member115, which slides on the outer diameter of the cylindrical shock tube104and the one axial end108, while the remaining connecting end member119is secured to a clevis mount138, the latter component being attached to the clevis sleeve134at the axial end112of the assembly housing102. According to this embodiment, each of the connecting end members117,119are clevises having a spherical bearing130disposed at their respective ends.

According to this embodiment, two (2) outer coil springs116are mounted in serial fashion onto the exterior of the assembly housing102and more specifically between a pair of end flanges120,124installed on the sleeve member115and the clevis sleeve134, respectively. A spring spacer128intermediately disposed on the exterior of the cylindrical shock tube104separates the two coil springs116, which when positioned thereon, are loaded in compression.

With reference toFIGS. 1 and 2, the connecting end member117fixedly retains one end of a piston assembly132that movably extends into the interior105of the assembly housing104. In operation and as later discussed in greater detail, the end of the connecting member117is attached to a movable door (not shown) or similar structure while the remaining connecting end member119is fixedly mounted, such as to an aircraft structure.

With reference toFIGS. 3A and 3B, one end112of the assembly housing102is defined by the clevis sleeve134as well as the clevis mount138, the clevis sleeve134being configured to engage one end of the connecting member119,FIG. 2. The clevis mount138is fixedly attached to one end of the cylindrical shock tube104. An accumulator spring142is disposed within an interior portion of the clevis mount138with one end of the accumulator spring142being attached to an end portion of an axially movable separator150(also herein referred to as the “accumulator piston”). The separator150is defined by an outer diameter that is slightly smaller than that of the inner diameter of the cylindrical shock tube104to permit limited axial movement of the separator150and the attached accumulator spring142. The separator150according to this embodiment further includes at least one peripheral sealing member156, such as an O-ring, formed in an annular exterior groove157thereof.

Still referring toFIGS. 3A and 3Band on the opposing side of the assembly (the left hand side of the cylindrical shock tube104according to the herein depicted figures), the piston assembly132and more specifically one end of a piston rod140is fixedly attached to the end connecting member117. The piston rod140extends into the hollow interior105of the cylindrical shock tube104and entirely through a fixed bearing member170, the latter being fixedly secured to one end of the shock tube104. The bearing member170according to this embodiment and as more clearly shown inFIG. 5retains a sealing wiper174and a wiper retainer177, each disposed within a center recess formed in the bearing member170, which is attached to the end of the shock tube104along with a peripheral seal member175disposed adjacent to the wiper retainer177.

The bearing member170has an outer diameter that is sized to sealingly engage the inner diameter of the cylindrical shock tube104. More specifically and according to this embodiment, the bearing member170includes at least one annular groove178on its exterior surface that receives a sealing element179, such as an elastomeric O-ring.

Still referring toFIG. 5, the piston assembly132further includes a piston head180that is attached to the exterior of a narrowed portion of the piston rod140. The piston head180is defined by an outer diameter that nearly matches that of the inner diameter of the shock tube104. An elastomeric sealing member184, such as an elastomeric quad ring or similarly formed member, is disposed within an annular groove188provided in the exterior surface of the piston head180. According to this embodiment, the piston head180includes a set of axial orifices190including a fixed orifice190A. Another of the orifices190B, according to this embodiment, includes a check valve196having a movable element, such as a ball that is disposed within an enlarged part of the orifice190B relative to an adjacent restricted area portion thereof, and in order to open and close depending on the direction of fluid flow, as discussed in greater detail herein.

As best seen inFIGS. 4-8, the piston rod140extends inwardly toward the accumulator piston150through a formed center opening of the piston head180and terminates at a distal end, the piston rod140further including a flat143disposed in relation to the fixed orifice190A of the piston head180. The sleeve-like member160is disposed over the extending end of the piston rod140, including a shelf or flange163adjacent to the piston head180. A cap member165is attached onto the distal end of the piston rod140by means of a nut or other fastener169and a spring means is disposed between the flange163of the sleeve-like member160and an inner facing surface of the cap member165. According to this embodiment, the spring means is a plurality of pre-loaded disc springs167. For the purposes discussed herein, the spring means can alternatively be at least one elastomeric spring, a coil spring or similar device capable of deflection and creating a storage of energy. More specifically, the disc springs167are compressively retained in a spacing that is created between the flange163and the inner facing surface of the cap member165on the exterior of the sleeve-like member160. The cap member165is further defined by a center opening that permits a distal end portion144of the piston rod140to extend therethrough in which the fastener169covers the distal end.

Still referring toFIGS. 4-8, the distal end144of the piston rod140further includes a small diameter bore145that partially extends into the interior of the piston rod140. This bore145terminates at a transversely extending bore147proximate the disc springs167, the latter bore terminating onto the defined flat143of the piston rod140.

A quantity of hydraulic fluid, such as silicone fluid, is added to the interior105of the assembly housing104through a fill plug158, the latter being axially provided on the separator150according to this embodiment, filling a hydraulic chamber220defined between the separator150and the piston assembly. Based on the movement of the piston assembly, the fluid is sealingly retained between the separator150and the bearing member170. As discussed herein, the hydraulic fluid is permitted to flow based on movement of the clevis/piston assembly within the interior of the actuator assembly100due to compressive and expansive movement thereof.

Operational details relating to the above actuator assembly100are herein described with further reference to the schematic figures depicted inFIGS. 4-8.

Referring toFIG. 4, one of the connecting end members117of the actuator assembly100(shown on the left) is connected to a door or other movable component under load (not shown) and the remaining connecting end members119of the assembly100(shown on the right) is fixedly retained such as a ground surface (such as an aircraft fuselage or related structure—also not shown).

As previously noted, the outer coil springs116are attached to the exterior of the assembly100and retained at their respective ends by end flanges120,124and the spring spacer128disposed between the two coil springs116according to this embodiment. It should be noted that the overall number of outer coil springs can be varied. For example, one or a plurality of springs can be alternatively utilized in order to provide the required forces. The outer coil springs116are maintained in compression according to this embodiment in order to properly urge the actuator assembly100, as herein described.

To review and according to this embodiment, the accumulator spring142is disposed in one end (the right end according to this embodiment) in relation to the end connecting member119along with an air chamber formed within the interior of the clevis sleeve134and clevis mount138. The piston assembly132is provided on the opposing side of the actuator assembly100, the piston assembly having the movable piston rod140and attached piston head180. The piston rod140is fixedly attached to the connecting end member117, wherein the piston head180includes a plurality of axial orifices190that permit movement of hydraulic fluid (not shown) therethrough relative to a hydraulic fluid chamber220disposed between the piston assembly132and the accumulator piston (separator150). The piston assembly132is sealingly attached to the interior of the assembly housing102and includes an energy absorber at its distal end adjacent the piston head180.

As previously noted, the energy absorber according to this version includes a plurality of disc springs167that are retained (pre-loaded) in compression within the spacing provided between the sleeve like member160and cap member165, the latter being attached to the distal end of the piston assembly132. The accumulator spring142provides movement due to volume displacement of the piston rod140into and out of the defined hydraulic fluid chamber220and also to compensate for thermal (temperature) effects on the overall actuator assembly100.

According to this embodiment, the distal end of the piston rod140further includes a defined small diameter bore145that extends intermediately to a transversely extending bore147, the latter further extending to the exterior of the piston rod140and on the defined flat143of the piston rod140, which is located in relation to the piston head180and the disposed disc springs167.

In operation and with reference toFIG. 5, and upon application of a compressive force upon the herein described assembly100, the piston assembly is caused into the interior of the assembly housing102, as illustrated per arrow234. As a result of this movement, fluid flows per arrow246from the hydraulic chamber220through the fixed orifice190A of the piston head180and opens the check valve196of the piston head180as fluid is caused to move in an opposing direction to that of the piston assembly132. More specifically, fluid is moved around the retained disc springs167and then through the orifices190of the piston head180. The sealing member188of the piston head180prevents flow of fluid other than through the defined orifices190, wherein the bearing member170and associated sealing members178prevents fluid from movement beyond the bearing member170. In the meantime, the outer coil springs116compress and create a biasing force against the applied load.

The volume of the piston rod140entering the fluid chamber220causes the accumulator piston150,FIG. 4, to move to the right toward the end112. In this mode, there is no restriction on fluid movement or in movement of the actuator assembly100with the only restrictive force being applied being the biasing force of the outer coil springs116. This allows the door (not shown) to be closed easily with minimal resistance from the damper.

As shown inFIG. 6, when the actuator assembly100is extended based on cessation of the applied load and through restoration by the outer coil springs116, the piston rod140is moved toward to the end of the assembly (as shown moving to the left by arrow250). Hydraulic fluid is therefore moved or directed through the fixed orifice190A of the piston head180, but not through the check valve190, which obstructs fluid movement as the piston head180is also moved to the left according to this Figure and providing a rate control to the movement of the assembly100. During this movement, the outer coil springs116extend to restore the assembly100to its pre-loaded condition. In this mode of operation, the piston rod volume exiting the hydraulic fluid chamber220moves the accumulator piston (separator150) toward the end108further aided by the biasing force of the accumulator spring142, restoring same to its original or home position. During extension of the actuator, the springs116push the attached door open and the damping force from the fluid flowing through the fixed orifice controls the opening rate of the door.

A full extension of the herein described actuator assembly100is depicted according toFIG. 7. In this mode of operation and as previously described, the check valve190prevents fluid movement through the piston head180and the only available movement of hydraulic fluid is through the fixed orifice190A. Movement of the piston assembly toward the end108of the assembly housing102is shown by arrow272. In the event that the fixed orifice190A of the piston head180becomes plugged or occluded according to this embodiment, accumulated fluid pressure moves the piston head180to the right, as shown per arrow274in which the accumulated pressure overcomes the compressive force of the disc springs167to permit this movement. This latter axial movement of the piston head180compresses the preloaded disc springs167, which therefore allows fluid flow, see arrow276, across the piston head180through the defined flat143in the piston rod140and through each of the bores147,145defined in the end of the piston rod144, the latter components acting as a pressure relief valve, to enable flow of fluid into the hydraulic fluid chamber220of the actuator assembly100. As in the preceding, the piston rod volume exiting the chamber220moves the accumulator piston130toward the end112of the assembly housing102.

Finally and as shown inFIG. 8, the herein described actuator assembly100is shown in its fully extended position in which the piston head180has already bottomed out on the bearing member170, see arrow280. In this position, the emergency door of the aircraft (not shown) would be fully open, but it is possible additional loads can be imparted to the door, such as high wind forces, with the door now outside of the fuselage. These forces would act to pull upon the piston rod140, as shown in the figure, wherein the set of disc springs167according to this embodiment are caused to compress, creating the deflection shown, towards the piston head180. The foregoing therefore creates a storage of energy based on the applied load to the actuator assembly100and a deflection D of the disc springs167as shown. This feature is also used to decelerate the door when it opens, as opposed to hitting a hard stop.

PARTS LIST FOR FIGS.1-8

It will be readily apparent that other variations and modifications are possible to those of sufficient skill and within the scope of the following claims.