LOCKING AND UNLOCKING MECHANISM

Abstract

A locking mechanism includes a linkage assembly having a first link (6a) and a second link (6b) joined at a pivot point (110). The assembly also includes a linkage assembly spring to bias the linkage assembly into a first, locked, position and a rotational rod (1) having a cam (120) formed thereon with a cam surface in engagement with the linkage assembly in the region of the pivot point (110). The assembly also includes a solenoid assembly (3) arranged, in a first mode, to rotate the rotational rod (1) 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.

Claims

1. 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.

2. The locking mechanism of claim 1, wherein said solenoid assembly in the first mode is de-energized and, in the second mode, is energized.

3. The locking mechanism of claim 1, wherein said solenoid assembly in the first mode is energized and, in the second mode, is de-energized.

4. An actuator lock bolt assembly comprising: a lock bolt movable between an actuator locking position and an actuator release position; and a locking mechanism as claimed in claim 1, arranged to secure the lock bolt in the actuator locking position in the first mode and to release the lock bolt to the actuator release position in the second mode, movement of the lock bolt being permitted in response to the linkage assembly being forced to the unlocked position.

5. An actuator assembly comprising: an actuator; and an actuator lock bolt assembly as claimed in claim 4, the actuator movable between a non-actuating position and an actuating position responsive to the lock bolt moving between the actuator locking position and the actuator release position.

6. A ram air turbine assembly comprising: a ram air turbine; and an actuator assembly as claimed in claim 5, the ram air turbine being movable between a stowed position and a deployed position responsive to the actuator moving between the actuating and the non-actuating position.

7. 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Preferred embodiments will now be described by way of example only and with reference to the accompanying drawings in which:

[0013] FIG. 1 shows a ram air turbine (RAT);

[0014] FIG. 2A shows a schematic view of a known linkage release mechanism, as described above, in the locked position;

[0015] FIG. 2B shows the mechanism of FIG. 2A in the unlocked position;

[0016] FIG. 3A is a perspective view of a locking mechanism according to the disclosure in the locked position;

[0017] FIG. 3B is a perspective view of the locking mechanism of FIG. 3A in the unlocking position;

[0018] FIG. 4 is an exploded view of the locking mechanism;

[0019] FIG. 5A is a simple diagram showing the positions of the mechanism components in the locked position;

[0020] FIG. 5B is a simple diagram showing the positions of the mechanism components in the unlocking position;

[0021] FIG. 6A is a cut-away view showing the positions of the mechanism components in the locked position; and

[0022] FIG. 6B is a cut-away view showing the positions of the mechanism components in the unlocking position.

DETAILED DESCRIPTION

[0023] FIG. 1 shows an RAT system 10 which is secured to an aircraft structure 12 by housing 14. The housing 14 pivotally supports a strut 16 having a turbine 18 at one end. The turbine 18 includes blades 20 which impart rotational drive to a generator 22 and a hydraulic pump 30, for example. An actuator 24 is secured to the strut at a first end 26 and to the housing at a second end 28. The actuator 24 is illustrated in its deployed position. The actuator 24 comprises a cylinder 32 which is biased by a spring 34 in order to deploy the strut 16. When the cylinder 32 is retracted, it is held in its retracted position by means of a locking mechanism, details of which will be described below.

[0024] 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.

[0025] In existing systems mentioned above, and shown in FIGS. 2A and 2B, pivoting of the toggle mechanism is permitted or prevented by means of the cross rod, that passes through the toggle mechanism, moved by the solenoids. A stop is required to prevent the toggle mechanism rotating further than desired.

[0026] Referring to FIGS. 3 to 6, the locking mechanism of the present disclosure comprises a lock bolt 100 that acts on the toggle mechanism 60 with the force F1 of a lock bolt spring (not shown). The force of the spring pushing against the toggle mechanism is biased to push the pivot point 110 to an overcentre position so that the toggle mechanism is not completely extended, and abuts against a cam 120 surface (120), thus locking movement of the lock bolt. If the actuator is to be moved, the locking mechanism needs to act against this overcentering to keep the links of the toggle mechanism extended at the pivot point 110.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] In the locked position, shown in FIGS. 3A, 4A, 5A and 6A, the solenoids are de-energised and so the cam 120 is in its neutral position. The lock bolt spring force F1 causes the lock bolt to push against the toggle mechanism links causing the mechanism to pivot upwards at pivot point 110. The cam 120 acts as a stop to prevent the toggle mechanism pivoting too far past the overcentre position.

[0031] To unlock the lock bolt (FIGS. 3A, 4A, 5A, 6A) the solenoid(s) (either both or just one) 3 are energised causing the rotating rod 1 to rotate in the direction of the arrow in FIG. 3B which, in turn, rotates the cam 120 causing it to push against the toggle links pushing the pivot point 110 down and moving it to a neutral or undercentre position. This allows the lock bolt to move against the force F1 of the spring to unlock the actuator. To lock the actuator in this position, the spring force F1 can be removed.

[0032] The release mechanism of the present disclosure provides improved operation of the linkage mechanism as compared to the arrangement of FIGS. 2A and 2B. The release mechanism operates on the same type of linkage assembly as shown in FIGS. 2A and 2B and has the same objective, i.e. to cause a downward movement of the linkage assembly to permit axial movement of the lock bolt

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] This mechanism could be easily adapted to existing actuators.

[0039] When the RAT is to be retracted to the stowed position, the lock bolt is moved in the opposition direction.

[0040] 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.

[0041] 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.