Actuator

Details Actuator Actuator

1999-11-22

2001-01-02

Thorpe, Timothy S. (Department: 2834)

Power plants

Reaction motor

Interrelated reaction motors

C074S424830, C074S089100

Utility Patent

active

06167694

ABSTRACT:

This invention relates to an actuator, and in particular to an actuator arranged to be driven by an electric motor. The invention is particularly suitable for use in aerospace applications, for example in driving the cowls of a thrust reverser system between their stowed and deployed conditions. It will be appreciated, that the invention is also applicable to other applications for example driving aircraft flaps or moving hatch doors, and may be used in non-aerospace applications.
A typical thrust reverser actuator is hydraulically driven between stowed and actuated positions. In order to move a thrust reverser cowl of a thrust reverser system, an initial high force must be applied by the actuator. After the initial movement of the cowl, the applied force can be reduced. However, typically, the applied force is not significantly reduced, the force applied by the actuator remaining at substantially its initial high level throughout the movement of the associated cowl. Clearly, this results in the system being relatively inefficient.
It is an object of the invention to provide an electrically driven actuator which obviates or mitigates this disadvantage.
According to the present invention there is provided an electrically driven actuator comprising a drive arrangement arranged to rotate a first, drive member, the first member being in screw-threaded engagement with a second member, the second member being in screw-threaded engagement with a third, output member, wherein the screw-threaded engagement between the first and second members is such that, when the first member rotates at a given speed relative to the second member, the second member moves axially relative to the first member at a first speed, the screw-threaded engagement between the second and third members being such that, when the second member rotates at the said given speed relative to the third member, the third member moves axially relative to the second member at a second, higher speed.
Where such an actuator is used to drive a cowl forming part of a thrust reverser system from a stowed position to a deployed position, the initial load applied to the third member by the cowl is high and substantially prevents rotational movement of the second and third members. As the second and third members do not rotate, rotation of the first member by the drive arrangement causes the second member to move axially at a low rate, thus commencing movement of the cowl. As the cowl moves, a point will be reached beyond which the load on the third member falls to a sufficiently low rate that relative movement between the second and third members can occur. Once this point is reached, the second member commences rotary movement with the first member, thus movement of the third member and the cowl occurs relative to the first and second members at a higher rate.
The second member conveniently comprises a dual rate nut, the first and third members comprising first and second screw-threaded rods, the first rod and corresponding part of the dual rate nut being provided with fine pitch screw threads, the second rod and corresponding part of the dual rate nut being provided with coarser pitch screw threads.
Preferably the screw threaded mechanisms are ball-screw mechanisms.
Desirably the relative axial movement of the first and second members is limited by abutment means whereafter in use continued rotation of the first member rotates the second member relative to the third member.
The invention further relates to an actuator system comprising a plurality of actuators of the type described hereinbefore, wherein the drive arrangements of the actuators are interconnected such that the actuators can be driven by a common electric motor. The invention still further resides in a thrust reverser system utilizing actuators or an actuator system as defined above for deploying cowls of the system.


REFERENCES:
patent: 2092563 (1937-09-01), Tucker
patent: 2674438 (1954-04-01), Dalton
patent: 2819589 (1958-01-01), Geyer
patent: 3203269 (1965-08-01), Perrine
patent: 4216909 (1980-08-01), Carlin
patent: 4519561 (1985-05-01), Timms
patent: 4953419 (1990-09-01), Schlenker
patent: 5303604 (1994-04-01), Mayfield
patent: 5848554 (1998-12-01), Kober et al.
patent: 0 552 129 (1993-07-01), None

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