Patent Application
20200369404
This application claims priority to European Patent Application No. 19461543.1 filed May 24, 2019, the entire contents of which is incorporated herein by reference.
The present disclosure relates to locking/unlocking mechanisms for deployable components. The mechanism is particularly suitable as an unlocking mechanism for a ram air turbine (RAT) actuator but could also find application in other deployable or movable systems such as other actuators, valves, pumps and the like.
Many systems and mechanisms are known in which a component is movable between a closed or stowed position and an open or deployed position, and wherein a component should be locked in the desired position and unlocked to permit movement between the positions. Particular examples are valves or actuators, such as RAT actuators as described in more detail below.
Ram air turbines are used in aircraft to provide electric and/or hydraulic power to components of the aircraft, for example in the event of failure of other electrical or hydraulic power generating equipment on board the aircraft. In normal operation of the aircraft, the RAT is housed within the aircraft, but when needed it is extended into the airflow around the aircraft such that it may turn, due to the airflow, and generates electrical and/or hydraulic power. The RAT is typically pivoted into position by means of an actuator, for example a hydraulic actuator. The actuator typically includes a bolt which extends to deploy the RAT. The actuator has a lock mechanism which prevents inadvertent movement of the bolt and, thus, inadvertent deployment of the RAT. The main locking mechanism typically comprises a spring loaded lock bolt which must be moved in an axial direction to unlock the actuator. Locking mechanisms are known from US2013/0327207, US2017/0260906, US 2017/0259934 and EP 3196127. RAT actuators are also disclosed in U.S. Pat. Nos. 8,640,563, 9,193,472, US 2015/0232195 and US 2015/0096437.
An unlocking mechanism is provided to permit the axial bolt movement. A conventional unlocking mechanism is shown, for example, in
The size and weight of components is of particular concern in aircraft where there is a desire to use lighter and smaller components, whilst maintaining safety and reliability.
One problem with such mechanisms is that they are very sensitive and must be accurately manufactured. Additional shimming is required in order to meet test procedure requirements and a stop has to be built into the mechanism to prevent the toggle tipping too far past the overcentre point.
There is, therefore, a need for a new locking mechanism that avoids these problems in the form of a simple, less expensive, less sensitive, but reliable mechanism.
According to one aspect, the disclosure provides a locking mechanism comprising a linkage assembly comprising: a first link and a second link joined at a pivot point; a linkage assembly spring to bias the linkage assembly into a first, locked, position; a rotational rod having a cam formed thereon with a cam surface in engagement with the linkage assembly in the region of the pivot point; a solenoid assembly arranged, in a first mode, to rotate the rotational rod such that the cam acts as a stop against the linkage assembly at the pivot point in a locked position, and, in a second mode to rotate the rotational rod such that the cam surface presses against the linkage assembly sufficiently to overcome the linkage assembly spring and to force the linkage assembly into a second, unlocked position.
In other aspects, the disclosure provides an actuator lock bolt assembly, an actuator assembly and a ram air turbine assembly incorporating such a mechanism.
In another aspect, there is provided a method of locking a lock bolt against axial movement and releasing the lock bolt to allow axial movement, the method comprising rotating a cam surface between a locked position where it secures a linkage assembly to prevent movement of the lock bolt and an unlocking position where the linkage assembly allows movement of the lock bolt.
Preferred embodiments will now be described by way of example only and with reference to the accompanying drawings in which:
The unlocking of the actuator is initiated by permitting movement of a lock bolt. This is made possible by means of a release (or unlocking) mechanism according to the present disclosure which will be described further below.
In existing systems mentioned above, and shown in
Referring to
The present invention replaces the cross rod of the prior art, passing through an aperture in the toggle mechanism, with a rotational rod or plunger 1 provided with a cam feature 120. The cam feature functions to block the toggle mechanism in the overcentre position when required and also to move the toggle mechanism to the undercentre position to permit movement of the actuator piston.
The rotational rod 1 is located at each end in a respective solenoid 3. Preferably the rod ends are mounted in bearing sleeves 2, preferably made of PTFE. The solenoids are preferably rotational solenoids arranged to rotate the rod 1.
One end of the toggle mechanism is engaged with the lock bolt. The other is attached to the inner wall of the actuator housing e.g. via a fixed clevis 40. The clevis 40 provides the pivot axis for the toggle mechanism and a return spring 5 that allows the toggle mechanism to return from the undercentre to the overcentre position.
In the locked position, shown in
To unlock the lock bolt (
The release mechanism of the present disclosure provides improved operation of the linkage mechanism as compared to the arrangement of
In the known systems, a pull-type solenoid actively pulls the cross-rod out of engagement with the stop against the spring force causing the linkage assembly to move away from, and hence release, the bolt. In contrast, in the arrangement of the present disclosure, a cam on a rotational rod is rotated by a solenoid to either lock the links in the locked position or push the links into the unlocking position.
As described above, in prior art arrangements, a cross-rod passing through the linkage assembly abuts against a stop to prevent movement of the lock bolt; to unlock the bolt, a pull solenoid acts against the spring force biasing the cross-rod towards the stop, to pull the cross-rod away from the stop, causing the linkage assembly to move out of engagement with, and permit axial movement of the lock bolt.
The present disclosure replaces the cross-rod with a cam formed on a rotational rod to cause the movement of the linkage assembly into and out of locking engagement with the lock bolt.
The example shown comprises two solenoids. It is also possible to have one or perhaps even more than two solenoids arranged on either side of the rotational rod to provide redundancy and extra engagement force. If two solenoids are used, the release mechanism reacts more quickly, and meets the requirements of aviation regulations for the duplication of critical systems.
In the examples described, in the locked position, the solenoid is de-energised. In an alternative embodiment the solenoid could be in the locked position when the solenoid was energised and in the unlocked position when the solenoid is de-energised.
This mechanism could be easily adapted to existing actuators.
When the RAT is to be retracted to the stowed position, the lock bolt is moved in the opposition direction.
The above is a description of a single embodiment by way of example only. Modifications may be made without departing from the scope of this disclosure.
While the apparatus has been described in the context of unlocking a RAT actuator, it may, as mentioned above, find use in other applications, for example of the types of actuator, valves, pumps or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19461543.1 | May 2019 | EP | regional |
