Blow down actuator assembly

1. An actuator assembly, comprising:

a drive assembly comprising a ball screw and a ball nut;

an actuation member;

a release member arranged inside of the actuation member;

a source of pressurized gas;

a securing mechanism, wherein the securing mechanism releasably locks the actuation member to the release member during a normal mode of operation; the securing mechanism configured to release the actuation member in response to an increase of pressure during an emergency mode of operation, the actuation member thereafter extends away from the release member and the actuation member extends away the ball screw and the ball nut of the drive assembly;

wherein during the normal mode of operation, the actuation member and the release member are engaged to move in unison; and

wherein during the emergency mode of operation, the pressurized gas automatically decouples the actuation member from the release member to move separately.

2. The actuator assembly of claim 1 , wherein the ball screw is configured with a raceway on a periphery thereof and ball nut housing bearings that ride on the raceway, the ball nut being coupled to the actuation member during the normal mode of operation such that a direction of rotation of the ball screw determines whether the actuation member extends or retracts from a housing.

3. The actuator assembly of claim 1 ,

wherein the securing mechanism comprises protrusions for engaging slots in the actuation member and the release member;

wherein a slot formed in the release member causes the protrusions of the securing mechanism to rotate through a slot formed in the actuation member; and

wherein the slot in the actuation member is formed to permit release of the actuation member from the securing mechanism.

4. The actuator assembly of claim 1 , further comprising a cover tube having an end cap and a seal plug.

5. The actuator assembly of claim 4 , further comprising a release piston that defines an expansion chamber between the release piston and the seal plug.

6. The actuator assembly of claim 5 , wherein when the pressurized gas is released into the expansion chamber, the release member is driven to unlock the securing mechanism, releasing the actuation member to move unrestrained past the release member.

7. The actuator assembly of claim 5 , wherein the source of pressurized gas is a gas generator housed internal to the actuator assembly.

8. The actuator assembly of claim 4 , further comprising an expandable retention ring housed toward a distal end of the cover tube, wherein the actuation member includes a circumferential retention groove, the expandable retention ring being biased to compress into the circumferential retention groove when the actuation member extends a predetermined distance from the end cap of the cover tube.

9. The actuator assembly of claim 8 , wherein the expandable retention ring comprises at least two ring pieces.

10. The actuator assembly of claim 9 , further comprising a nut adapter coupled to the ball nut and the release member, the nut adapter being configured with a release mechanism for expanding the expandable retention ring when the release member is secured to the actuation member.

11. The actuator assembly of claim 10 , wherein the release mechanism includes ramped extensions configured onto the nut adapter.

12. The actuator assembly of claim 5 , wherein the ball screw is hollow and the pressurized gas is delivered through the ball screw to the expansion chamber during the emergency mode of operation.

13. The actuator assembly of claim 2 , further comprising a motor and a gear train for driving the ball screw to extend and retract the actuation member during the normal mode of operation.

14. An electro-mechanical actuator comprising:

an electro-mechanical drive system comprising a ball screw and a ball nut;

an actuation member;

a release member arranged inside of the actuation member;

an integrated backup system operated by pressurized gas comprising a securing mechanism;

the securing mechanism releasably locks the actuation member to the release member during a normal mode of operation; and

the securing mechanism configured to release the actuation member in response to an increase of pressure during an emergency mode of operation, the actuation member thereafter extends away from the release member and the actuation member extends away the ball screw and the ball nut of the electro-mechanical drive system,

wherein when the backup system is activated, the electro-mechanical drive system is decoupled from the actuation member and the actuation member moves to a predetermined position and mechanically locks in place.

15. The electro-mechanical actuator of claim 14 , wherein the electro-mechanical drive system includes the ball screw configured with a raceway on a periphery thereof and ball nut housing bearings that ride on the raceway, the ball nut being coupled to drive the actuation member during the normal mode of operation.

16. The electro-mechanical actuator of claim 14 , wherein the pressurized gas is pressurized nitrogen.

17. The electro-mechanical actuator of claim 14 , wherein the electro-mechanical drive system comprises a release piston that defines an expansion chamber for receiving the pressurized gas.

18. The actuator of claim 14 , further comprising a locking assembly for mechanically locking the actuation member when the drive system is decoupled, the locking assembly including an expandable retention ring biased to engage a ring groove on a drive arm of the drive system.

19. The electro-mechanical actuator of claim 18 , wherein the expandable retention ring comprises at least two ring pieces.

20. A landing gear unit for an airplane including the electro-mechanical actuator according to claim 14 , wherein a controlled member comprises landing gear.