Blow down actuator assembly

An actuator assembly includes an actuation member, a release member, and a source of pressurized gas, wherein during a normal mode of operation, the actuation member and the release member are engaged to move in unison, and wherein during an emergency mode of operation, pressurized gas automatically decouples the actuation member from the release member to move separately. In accordance with yet other aspects of the present disclosure, an electro-mechanical actuator includes an electro-mechanical drive system and an integrated backup system operated by a gas generator, wherein when the backup system is activated, the electro-mechanical drive system is decoupled and the actuator moves to a predetermined position and mechanically locks in place.

CROSS REFERENCE TO PRIOR APPLICATIONS

This application is a continuation of International Application No. PCT/US2013/044068, filed Jun. 4, 2013 and designating the U.S., which claims priority to provisional Patent Application No. 61/655,331, filed Jun. 4, 2012, both of which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to actuator mechanisms, more particularly to an actuator assembly having an integrated emergency backup system.

BACKGROUND OF THE INVENTION

Mechanical linear actuators are used for translating rotational motion to linear motion. For example, ball screws are linear actuators that rely on a threaded shaft and a nut housing. The nut housing typically contains ball bearings that engage a helical raceway defined by the threaded shaft. Thus, rotational movement of the shaft translates into linear movement of the nut housing along the shaft. These types of linear actuators are often used in aeronautical applications, for example, to control movement of control surfaces, open and close windows, doors and/or access panels, and control the extension of landing gear. Linear actuators are also often used to convert rotary motion from an electric motor to axial movement of a steering rack in vehicular power steering systems and for precision control in robotic manufacturing.

Particularly in aeronautical applications, the failure of a mechanical linear drive system can have catastrophic consequences. The failure of one or more aspects of the drive system, such as the motor, the gear train, or the ball screw drive, may result, for example, in the landing gear of an airplane failing to extend or to extend into a fully locked open position. Accordingly, emergency systems are often provided that override and/or bypass the mechanical linear drive system to address such failures. However, these systems are often separate assemblies from the drive assembly, requiring additional space and hardware to accommodate the assembly. There is a need and desire for an actuator assembly that has an integrated emergency system, a system that automatically decouples aspects of the system from the normal drive configuration during an emergency.

SUMMARY OF THE INVENTION

Embodiments of the present invention advantageously provide an actuation assembly and methods of use thereof. A preferred embodiment of an actuator assembly includes an actuation member, a release member, and a source of pressurized gas, wherein during a normal mode of operation, the actuation member and the release member are engaged to move in unison, and wherein during an emergency mode of operation, pressurized gas automatically decouples the actuation member from the release member to move separately.

In accordance with yet other aspects of the present disclosure, an electro-mechanical actuator includes an electro-mechanical drive system and an integrated backup system operated by a gas generator, wherein when the backup system is activated, the electro-mechanical drive system is decoupled and the actuator moves to a predetermined position and mechanically locks in place.

DETAILED DESCRIPTION

The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout.

Various aspects of an actuator assembly may be illustrated by describing components that are coupled, attached, and/or joined together. As used herein, the terms “coupled”, “attached”, and/or “joined” are used to indicate either a direct connection between two components or, where appropriate, an indirect connection to one another through intervening or intermediate components. In contrast, when a component is referred to as being “directly coupled”, “directly attached”, and/or “directly joined” to another component, there are no intervening elements present.

Relative terms such as “lower” or “bottom” and “upper” or “top” may be used herein to describe one element's relationship to another element illustrated in the drawings. It will be understood that relative terms are intended to encompass different orientations of an electric strike assembly in addition to the orientation depicted in the drawings. By way of example, if aspects of an actuator assembly shown in the drawings are turned over, elements described as being on the “bottom” side of the other elements would then be oriented on the “top” side of the other elements. The term “bottom” can therefore encompass both an orientation of “bottom” and “top” depending on the particular orientation of the apparatus.

FIGS. 1-4illustrate multiple views of an assembled blow down actuator assembly100in accordance with aspects of the present invention. The actuator assembly100may include an electric motor110operably connected to a drive assembly200via a gear train housed in a gear housing300. A mounting device120, such as a bracket or any other suitable mounting mechanism, may be provided on a surface of the gear housing300for mounting the actuator assembly100to a stable support structure, such as the body structure of an airplane. The drive assembly200includes a drive arm assembly202for actuation of a controlled member, such as a control surface, door or a landing gear, for example. A distal end of the drive arm assembly202may be provided with a connection device204, such as an eye bolt rod or any other suitable connection device, for connecting the drive arm assembly202to the controlled member.

As shown inFIG. 2, the actuator assembly may be modular, wherein each of the major components, such as the motor110and the drive assembly200, for example, may be separately and independently attached and/or detached from the gear housing300for ease of maintenance and/or replacement. A motor mounting plate112and/or a drive assembly mounting plate206may be provided for mounting the motor110and the drive assembly200to the gear housing300via attachment means, such as bolts or screws.

FIG. 3is a side view of the actuator assembly shown inFIGS. 1 and 2.FIG. 4provides a cross-sectional view of the actuator assembly100taken along the cross-sectional plane A-A ofFIG. 3. The motor110may have a central drive shaft114that is operably connected through gears116and118to drive a ball screw208of the drive assembly200. The drive assembly200has a cover tube210and end cap212. The end cap212has a central orifice214through which the drive arm assembly202slidably extends. A ball nut216may be situated on the ball screw208such that, during normal operation of the drive assembly200, rotation of the ball screw208forces the ball nut216via housed bearings217to travel along the raceway defined by the threading on the ball screw208. The direction of rotation of the ball screw208determines whether the drive arm assembly202extends or retracts through the orifice214.

A nut adapter218may be provided on a distal end of the ball nut216. The nut adapter218may be formed with one or more notched seats220for seating one or more end portions222of one or more release levers224. The release levers224may be rotatably mounted on a release cap226, as described in further detail below.

The release cap226may be fixed to an actuation tube230, which is the primary longitudinal body component of the piston-like drive arm assembly202. A release tube234may be concentrically arranged inside of the actuation tube230. A locking ring236is provided that releasably engages the release tube234and the actuation tube230. The release tube234extends longitudinally within the actuation tube230to abut a release piston238. The release piston238houses a gas generator240. As shown inFIG. 4, a distal end of the actuation tube230extends beyond the release tube234and the release piston238when the release tube234and the actuation tube230are engaged in a locked position via the locking ring236.

A sealing plug244is provided to close the distal end of the actuation tube230. The sealing plug244may abut the release piston238during normal operation of the drive assembly200. An expansion chamber250may be defined between the release piston238and the sealing plug244. For example, the release piston238and/or the sealing plug244may be formed with a recessed area252to form the expansion chamber250. The connection device204may be mounted, such as by press fit or via a threaded connection, for example, to the sealing plug244, or may alternatively be integrally formed with the sealing plug244. Multiple o-rings254or other suitable sealing mechanisms may be used to ensure that the expansion chamber250is completely sealed.

In accordance with other aspects of the present disclosure, the cover tube210may be provided with a locking channel256, or any other suitable detent means, on an interior surface toward the distal end. As will be explained in greater detail below, the locking channel256may engage the release levers224during emergency operation of the actuator assembly100.

FIGS. 5-7illustrate operation of the actuator assembly100during a normal mode, in which the motor110controls the drive assembly200to extend and/or retract the drive arm assembly202.FIGS. 5 and 6are illustrated with the cover tube210and gear housing removed to assist in an understanding of the operation of the internal components.

In particular,FIG. 5illustrates the assembly100with the drive arm assembly202in a fully retracted position. To control movement of a controlled device, e.g., a landing gear, a signal may be sent to the motor110to extend the drive arm assembly202to a predetermined position, which may be fully extended and/or any position in between. As shown inFIG. 6, the motor110operates through the gear train to turn the ball screw208, which in turn causes the ball nut216to extend along the shaft of the ball screw208, pushing the drive arm assembly202to extend.

As shown inFIG. 7, in a normal mode of operation, the locking ring236is fully engaged with both the actuation tube230and the release tube234. As such, the ball nut216, the nut adapter218, the actuation tube230, and the release tube234are all engaged to move in unison as one assembly. The assembly may thus slide within the cover tube210to a desired position. Because the drive arm assembly moves in unison, the end portions222of the release levers224remain seated in a closed position between the seat220and the cover tube210.

The release levers224may be mounted to the release cap226by a spring loaded hinge228having a spring load forcing the end portions222toward the seats220. Thus, during normal operation, the catch ends223of the release levers224will not engage the locking channel256of the cover tube210. The catch ends223of the release levers224may only be released to engage the locking channel256if the end portions222are unseated from the seats220to permit the spring force of the hinges228to rotate the catch ends223outward. In this manner, during normal mode operation, the drive arm assembly202may be extended to a fully open position without the actuator assembly100being locked by the release levers224in the fully open position. The drive arm assembly202may thus be retracted from a fully open position as desired.

FIGS. 7-13illustrate an emergency mode of operation of the actuator assembly100, during which aspects of the normal drive assembly are automatically decoupled to permit an emergency extension of the actuation tube230into a fully extended, locked position. For example, if during flight there is a malfunction of a component of the actuator assembly100, such as the motor, the gear train, and/or the ball screw/ball nut, the landing gear may be prevented from achieving full extension. Accordingly, in this situation, the emergency mode of operation of the actuator assembly100could be automatically initiated or, for example, manually initiated by a pilot. As shown inFIG. 7, if the emergency mode is initiated, a signal may be electrically sent to the gas generator240to initiate an emergency sequence. In accordance with other aspects of the disclosure, the emergency mode may be activated by any suitable means, including mechanical actuation methods having an activation switch, such as a piezo switch or a firing pin. In accordance with yet other aspects of the present disclosure, the ball screw208may be hollow to permit a wire to carry the activation signal to the gas generator240. The signal may initiate a process in the gas generator240that, for example, similar to conventional airbag devices, mixes sodium azide (NaN3) and potassium nitrate (KNO3) in a reaction that produces a large burst of hot nitrogen gas. The rapid expansion of the nitrogen gas is released into the expansion chamber250. In yet other aspects of the present disclosure, the gas generator240may release any combination of chemicals, for example, that are known to rapidly release a supply of pressurized fluid into the expansion chamber250. In accordance with yet other aspects of the present disclosure, conventional combustion techniques may be used to generate the necessary rapid pressure increase in the expansion chamber250as a result of activation of activation of the emergency backup system.

The rapid release of pressurized fluid into the expansion chamber250simultaneously produces pressure against the release piston238and the sealing plug244. The release piston238may be formed with a flanged portion260. When pressure is applied against the release piston238, the flanged portion260engages the distal end of the release tube234to force the release tube234to slide in a direction towards the nut adapter218and the locking ring236. As shown inFIG. 7, during normal operation, a space235exists between a proximal end of the release tube and the nut adapter218. The space235allows room for the release tube234to release backward during emergency operation.

As shown in the cutaway view ofFIG. 8, the locking ring236may be formed with protrusions237for engaging slots in the actuation tube230and the release tube234. As shown in close-up series inFIGS. 9-11, as the release tube234is forced back by the increasing pressure in the expansion chamber250, a slot264formed in the release tube234causes the protrusions237of the locking ring236to rotate through a slot266formed in the actuation tube230. The slot266in the actuation tube is formed to permit release of the actuation tube230from the lock ring236once the lock ring236rotates through to the position shown inFIG. 11. A spring270may be provided to maintain tension on the release tube234to prevent premature actuation due to jarring and/or vibration.

The release tube234is formed to remain engaged with the lock ring236throughout the emergency activation procedure. Accordingly, once the actuation tube230reaches the position shown inFIG. 11, as shown inFIG. 12, the actuation tube230is free to extend, sliding past the locked release tube234and permitting the expansion chamber250to expand under pressure from the gas generator240. As the actuation tube230extends, the release cap226mounted thereon also slides away from the screw nut216and the nut adapter218, which remain locked in position by the release tube234. The end portions222of the release levers224are thus freed from the seats220and may rotate inward under spring force from the spring loaded hinges228. However, the cover tube210prevents rotation of the release levers224until, as shown inFIG. 13, the actuation tube230is in a fully extended position. At the fully extended position, the catch ends223of the release levers224are free to rotate into the locking channel256. The actuation tube230may thus be prevented from sliding back into the cover tube210and the actuator assembly100locked in the fully extended position.

Of the many advantages of the present disclosure, activation of the emergency procedure may be initiated regardless of the stroke position of the drive arm assembly202. As such, even if failure occurs during normal operation, midway through a procedure such as the lowering of landing gear, emergency activation of the blow down actuator assembly100automatically decouples those aspects of the assembly100associated with the normal drive mode and permits full extension of the actuation tube230into a locked position via those aspects of the assembly100associated with the integrated emergency backup system.

In accordance with yet other aspects of the present disclosure, a pressure relief valve may be provided to relieve excess pressure from the expansion chamber250, particularly in the event the emergency mode is activated when the normal drive system has the drive arm assembly202in a nearly extended position. In that case, the expansion chamber250will not need to expand nearly as much as during the situation when the drive arm assembly202is in a substantially retracted position.

In accordance with yet another aspect of the present disclosure, the integrated emergency back-up actuation system described herein may be applied to non-linear actuator drive assemblies, for example, a rotary actuator.

FIGS. 14 and 15illustrate an assembled blow down actuator assembly1100in accordance with yet other aspects of the present invention. The actuator assembly1100may include an electric motor1110operably connected to a drive assembly1200via a gear train housed in a gear housing1300. A mounting device1120, such as a bracket or any other suitable mounting mechanism, may be provided on a surface of the gear housing1300for mounting the actuator assembly1100to a stable support structure, such as the body structure of an airplane. The drive assembly1200includes a drive arm assembly1202for actuation of a controlled member, such as a control surface, door or a landing gear, for example. A distal end of the drive arm assembly1202may be provided with a connection device1204, such as an eye bolt rod or any other suitable connection device, for connecting the drive arm assembly1202to the controlled member.

The actuator assembly may be modular, wherein each of the major components, such as the motor1110and the drive assembly1200, for example, may be separately and independently attached and/or detached from the gear housing1300for ease of maintenance and/or replacement. A motor mounting plate1112and/or a drive assembly mounting plate1206may be provided for mounting the motor1110and the drive assembly1200to the gear housing1300via attachment means, such as bolts or screws.

FIG. 15provides a cross-sectional view of the actuator assembly1100. The motor1110may have a central drive shaft1114that is operably connected through gears1116and1118to drive a ball screw1208of the drive assembly1200. The drive assembly1200has a cover tube1210and end cap1212. The end cap1212has a central orifice1214through which the drive arm assembly1202slidably extends. A housing1211for an expandable retaining ring assembly1213may be configured toward the distal end of the cover tube1210.

A ball nut1216may be situated on the ball screw1208such that, during normal operation of the drive assembly1200, rotation of the ball screw1208forces the ball nut1216via housed bearings1217to travel along the raceway defined by the threading on the ball screw1208. The direction of rotation of the ball screw1208determines whether the drive arm assembly1202extends or retracts through the orifice1214.

A nut adapter1218may be provided on a distal end of the ball nut1216. An actuation tube1230, which is the primary longitudinal body component of the piston-like drive arm assembly1202may be concentrically arranged around a release tube1234. The release tube1234extends longitudinally within the actuation tube1230to abut a release piston1238. A distal end of the actuation tube1230extends beyond the release tube1234and the release piston1238when the release tube1234and the actuation tube1230are engaged in a locked position via a securing mechanism, and a proximal end of the actuation tube1230may be configured with a retention groove1231.

A sealing plug1244is provided to close the distal end of the actuation tube1230. The sealing plug1244may abut the release piston1238during normal operation of the drive assembly1200. An expansion chamber1250may be defined between the release piston1238and the sealing plug1244. For example, the release piston1238and/or the sealing plug1244may be formed with a recessed area1252to form the expansion chamber1250. The connection device1204may be mounted, such as by press fit or via a threaded connection, for example, to the sealing plug1244, or may alternatively be integrally formed with the sealing plug1244. Multiple o-rings or other suitable sealing mechanisms may be used to ensure that the expansion chamber1250is completely sealed.

FIGS. 16 and 17illustrate operation of the actuator assembly1100during a normal mode, in which the motor1110controls the drive assembly1200to extend and/or retract the drive arm assembly1202.FIGS. 16 and 17are illustrated with the cover tube1210and gear housing removed to assist in an understanding of the operation of the internal components.

In particular,FIG. 16illustrates the assembly1100with the drive arm assembly1202in a fully retracted position. To control movement of a controlled device, e.g., a landing gear, a signal may be sent to the motor1110to extend the drive arm assembly1202to a predetermined position, which may be fully extended and/or any position in between. As shown inFIG. 17, the motor1110operates through the gear train to turn the ball screw1208, which in turn causes the ball nut1216to extend along the shaft of the ball screw1208, pushing the drive arm assembly1202to extend.

As shown inFIGS. 18 and 19, the actuation tube1230and the release tube1234may be engaged by a retaining pin1215that slides in a slot1219provided in the nut adapter1218. In a normal mode of operation, the retaining pin1215ensures that both the actuation tube1230and the release tube1234are fully engaged such that the ball nut1216, the nut adapter1218, the actuation tube1230, and the release tube1234are all secured to move in unison as one assembly. The assembly may thus slide within the cover tube1210(not shown inFIGS. 18 and 18) to a desired position.

The nut adapter1218may be formed with ramped extensions1221. The function of the ramped extensions1221is explained in further detail below. However, during normal operations, the ramped extensions1221prevent the expandable retaining ring assembly1213from engaging the retention groove1231on the actuation tube1230.

FIGS. 20-22illustrate an emergency mode of operation of the actuator assembly1100, during which aspects of the normal drive assembly may be automatically decoupled to permit an emergency extension of the actuation tube1230into a fully extended, locked position. For example, if during flight there is a malfunction of a component of the actuator assembly1100, such as the motor, the gear train, and/or the ball screw/ball nut, the landing gear may be prevented from achieving full extension. Accordingly, in this situation, the emergency mode of operation of the actuator assembly1100could be automatically initiated or, for example, manually initiated by a pilot. Referring back toFIG. 15, if the emergency mode is initiated, a signal may be electrically sent to actuate a source of pressurized gas into the hollow tube portion of the ball screw1208. In accordance with other aspects of the disclosure, the emergency mode may be activated by any suitable means, including mechanical actuation methods having an activation switch, such as a piezo switch or a firing pin. Any suitable pressurized gas, such as nitrogen, may be provided from a pressurized gas source, such as a gas generator (not shown), attached to or situated near the assembly1100or connected by a conduit for delivery from any external location. Various types of pressure connection fittings for attachment of a pressure conduit may be configured into the assembly to allow for quick attachment or detachment to the source of pressurized gas. The pressurized gas may be delivered into the proximal end of the hollow tube portion of the ball screw1208, and forced into the expansion chamber1250.

The rapid release of pressurized fluid into the expansion chamber1250simultaneously produces pressure against the release piston1238and the sealing plug1244. As shown inFIG. 14, the release piston1238may be formed with a flanged portion1260. When pressure is applied against the release piston1238, the flanged portion2160engages the distal end of the release tube1234to force the release tube1234to slide in a direction towards the nut adapter1218and the retaining pin1215. As shown inFIGS. 20 and 21, as the release tube1234is forced in a rearward direction by the increasing pressure in the expansion chamber1250, the retaining pin1215slides in the slot on the nut adapter1218and forces the release tube1234to rotate into a position in which the actuation tube1230is free to disengage from the release tube1234and the nut adapter1218. Detents, grooves, a spring pin, and/or any suitable means for permitting disengagement of the actuation tube1230from the release tube1234may be used. Accordingly, as shown inFIG. 22, with the actuation tube1230disengaged from the release tube1234and the nut adapter1218, the actuation tube1230is free to extend due to the pressure increasing the expansion of the expanding chamber1250. A spring1270(seeFIGS. 20 and 21) may be provided to maintain tension on the release tube1234to prevent premature actuation due to jarring and/or vibration.

The release tube1234is formed to remain engaged with the nut adapter1218and the screw nut1216via the retaining pin1215throughout the emergency activation procedure. The actuation tube1230extends until, as shown inFIG. 23, the retention groove1231on the actuation tube1230enters the housing1211wherein the expandable retaining ring assembly1213is forced by biasing means to compress into the retention groove1231for locking the actuation tube1230into an fully extended position. The expandable retaining ring assembly1213may be configured to be four quarter circle ring pieces for example, which are spring actuated into a biasing position toward the actuation tube1230. During normal operation, the expandable retaining ring assembly1213, or the components thereof, is prevented from compression by the exterior wall of the actuation tube1230. As illustrated inFIG. 26, for example, the ramped extensions1221on the nut adapter1218are formed to align with grooves1229configured at predetermined locations on the free end periphery of the actuation tube1230. During normal operation (refer back toFIG. 17), the ramped extensions1221are seated in the grooves1229and extend across the retention groove1231. As such, when the actuation tube1230, the release tube1234, and the nut adapter1218slide toward housing1211, the ramped extensions1221prevent the retaining ring assembly1213from compressing into the retention groove1231. Thus, during normal operation, the ramped extensions1221permit proper retraction of the actuation tube1230.

However, as shown inFIGS. 24-26, in accordance with yet other aspects of the present invention, the ramped extensions1221on the nut adapter1218are also configured to disengage an engaged retention ring1213to permit a reset of the actuator assembly1100once the emergency situation is resolved. In combination with the absence of a gas generator internal to the actuator assembly1100, the blow down actuator assembly1100does not thus require complete disassembly and reassembly to reset for the next emergency operation.

As shown inFIGS. 24-26, to reset the actuator assembly1100, the ball screw1208may be actuated to move the ball nut1216, nut adapter1218, and release tube1234as a unit toward the actuation tube1230that is locked in the extended position by the retention ring1213being biased into the retention groove1231. The ramped extensions1221slide toward the housing1211and into the grooves1229(seeFIG. 25). Continued turning of the ball screw1208forces the ramped extensions1221to push under and expand the expanding ring assembly1213to disengage the ring assembly1213from the ring groove1231. The release tube1234may thus reengage the actuation tube1230such that the entire arm assembly, now assembly, is reset and may be retracted into housing1210to operate under normal conditions. The procedure may be repeated as necessary as long as a pressure source is replaced or configured to supply pressurized gas to the assembly1100during a subsequent emergency situation.

Of the many advantages of the present disclosure, activation of the emergency procedure may be initiated regardless of the stroke position of the drive arm assembly1202. As such, even if failure occurs during normal operation, midway through a procedure such as the lowering of landing gear, emergency activation of the blow down actuator assembly1100automatically decouples those aspects of the assembly1100associated with the normal drive mode and permits full extension of the actuation tube1230into a locked position via those aspects of the assembly1100associated with the integrated emergency backup system.

In accordance with yet other aspects of the present disclosure, a pressure relief valve may be provided to relieve excess pressure from the expansion chamber1250, particularly in the event the emergency mode is activated when the normal drive system has the drive arm assembly1202in a nearly extended position. In that case, the expansion chamber1250will not need to expand nearly as much as during the situation when the drive arm assembly1202is in a substantially retracted position.