LOCKING AND UNLOCKING MECHANISM FOR RAM AIR TURBINE

Abstract

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 cam assembly having a cam 1 with a cam surface in engagement with the linkage assembly; a cam biasing member such as a spring arranged to bias the cam surface to press against the linkage assembly sufficiently to overcome the linkage assembly spring and to force the linkage assembly into a second, unlocked position; and a solenoid assembly arranged to engage the cam in a locked position in which the cam is prevented from forcing the linkage assembly into the 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 cam assembly having a cam with a cam surface in engagement with the linkage assembly; a cam biasing member arranged to bias the cam surface to press against the linkage assembly sufficiently to overcome the linkage assembly spring and to force the linkage assembly into a second, unlocked position; and a solenoid assembly arranged to engage the cam in a locked position in which the cam is prevented from forcing the linkage assembly into the unlocked position.

2. The locking mechanism of claim 1, wherein said solenoid assembly comprises a solenoid plunger having a plunger tip wherein, in the locked position, the plunger tip is in locking engagement with the cam to prevent the cam from being pressed against the linkage assembly by the force of the cam biasing member.

3. The locking mechanism of claim 2 wherein, in the locked position, the plunger tip engages in a detent in the cam.

4. The locking mechanism of claim 2, wherein said solenoid assembly further comprises a spring arranged to bias the plunger tip into engagement with the cam when the solenoid is de-energised and out of engagement with the cam when the solenoid is energised.

5. The locking mechanism of claim 2, wherein said solenoid assembly further comprises a spring arranged to bias the plunger tip into engagement with the cam when the solenoid is energised and out of engagement with the cam when the solenoid is de-energised.

6. The locking mechanism of claim 1, further comprising a second solenoid assembly arranged on an opposite of the cam assembly to said solenoid assembly.

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 typical linkage release mechanism in the locked position;

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

[0016] FIGS. 3a and 3b show a side view of the release mechanism of the present disclosure.

[0017] FIG. 4 shows a perspective view of the mechanism shown in FIGS. 3a and 3b.

[0018] FIGS. 5a-5c show the operation of the mechanism shown in FIGS. 3 and 4.

DETAILED DESCRIPTION

[0019] 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.

[0020] The unlocking of the actuator is initiated by permitting movement of the lock bolt 38. This is made possible by means of a release mechanism according to the present disclosure which will be described further below.

[0021] FIGS. 3a and 3b show a schematic view of the release mechanism of the present disclosure.

[0022] FIG. 3a shows the release mechanism in the locked position where axial movement of the lock bolt is prevented and, in FIG. 3b, in the unlocked position permitting movement of the lock bolt for deployment of the actuator.

[0023] FIG. 4 shows a perspective view of the arrangement of FIGS. 3a and 3b.

[0024] The release mechanism of the present disclosure provides improved operation of the linkage mechanism as compared to the pull solenoid 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

[0025] 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 is held in its engaged position by the tip of a solenoid plunger engaging in the cam(s).

[0026] 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.

[0027] The present disclosure replaces the pull solenoid and cross-rod with a cam assembly to cause the movement of the linkage assembly into and out of locking engagement with the lock bolt.

[0028] As can be seen, for example, in FIGS. 3a) and 3b), in a first, locked position, a cam 1 makes surface 1a contact with a first link 2a of the linkage assembly 2, but, as the cam is locked in position by one or more solenoid assemblies 3 (described further below), it does not exert force against the link to overcome the spring force M causing the link to pivot upwards, this causes the pivot point 4 between the first and second link 2b to take an upper position and the second link to extend to engage with, and prevent axial movement of the lock bolt 38 (as with the cross-bar abutting against the stop in existing systems).

[0029] To move the linkage assembly out of engagement with the lock bolt, to allow movement of the lock bolt, the cam is released by the solenoid(s) (described further below). A cam biasing member such as a spring 5 acting against the cam has sufficient force to overcome the force of the linkage assembly spring and this forces the cam downwards to push, at cam surface 1a, against the first link. The first link thus pivots downwards about the pivot point, causing the second link to pivot upwards and out of engagement with the lock bolt. The lock bolt is then able to move axially.

[0030] In the perspective view of FIG. 4, it can be seen that the solenoid is de-energised and a solenoid spring biases the solenoid plunger tip into locking engagement with the cam so as to prevent rotation of the cam.

[0031] The solenoid assembly for locking/releasing the cam can be seen in FIGS. 5a to 5c. The examples show two solenoid assemblies acting on the cams. It is also possible to have just one assembly or, indeed, more than two.

[0032] The solenoid assembly comprises a solenoid 6, a solenoid plunger 7, a solenoid spring, biasing the plunger, and a solenoid plunger tip 8.

[0033] In the locked position, the solenoid is de-energised and so the solenoid spring biases the plunger, and hence the plunger tip, towards the cam such that the plunger tip engages with the cam, e.g. by engaging in an aperture or detent in the cam. This holds the cam such that it cannot move under the force of the cam spring to press against the linkage assembly.

[0034] To release the lock bolt, as shown in FIGS. 5a to 5c, the solenoid is energised, causing the plunger, and hence the plunger tip, to move against the bias of the solenoid spring, moving the tip out of engagement with the cam, the cam is then released to move under the force of the cam spring, moving the first link 2a away from the stop position and thus the linkage assembly 2 away from the bolt, allowing axial movement of the bolt.

[0035] 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 cams 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.

[0036] 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.

[0037] This mechanism could be easily adapted to existing actuators.

[0038] When the RAT is to be retracted to the stowed position, the lock bolt 38 is moved in the opposition direction.

[0039] 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.

[0040] 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.