GB2426283A

GB2426283A - Lock mechanism with damage indication

Info

Publication number: GB2426283A
Application number: GB0609929A
Authority: GB
Inventors: Daniel Henry Roberts
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 2005-05-21
Filing date: 2006-05-19
Publication date: 2006-11-22
Anticipated expiration: 2026-05-19
Also published as: GB2426283B; GB0609929D0; GB0510424D0

Abstract

A locking mechanism for a thrust reverser door 3, 4 or the like has a locking arm 11 pivoted on an axle 12 midway along its length and has a hook portion 21 at one end. The other end 16 of the locking arm 11 is coupled with an actuator 12 by which the locking arm can be rotated about its axle to move the hook portion into or out of locking engagement with a locking pin 7 on the thrust reverser door. The locking arm 11 supports a follower 13, which is also rotatable on the axle 12 and can be rotated relative to the locking arm to an extent limited by a stop 27 on the hook portion 21. A finger 36 on the follower 13 contacts a sensor 14 to indicate that the locking arm 11 is in a locking position (fig. 2). If the hook portion 21 of the locking arm 11 carrying the stop 27 should break off (fig. 6), a spring 32 moves the follower 13 to a position out of contact with the sensor 14 even though the locking arm is in a locking position.

Description

RESTRAINING MECHANISMS

This invention relates to restraining mechanisms.

The invention is more particularly concerned with restraining mechanisms of the kind including a restraining member and means to provide an indication of the position of the restraining member.

Thrust reversers on aircraft gas-turbine engines are used to assist braking of an aircraft during landing by redirecting a part of the engine by-pass flow forwardly relative to the aircraft. The thrust reversers commonly have one or more doors displaced by actuators to an open position where they project into the by-pass flow through the engine so that a part of the gas flow is diverted forwardly. The thrust reversers also have some form of lock or restraining mechanism operable to hold the doors closed. The lock is released when the doors need to be opened. It is usual to provide some form of sensor, such as a microswitch, responsive to the position of the lock, so that an indication is given if the lock should fail to disengage.

These previous arrangements, therefore, indicate correct engagement of the lock if the lock is in the appropriate position. However, a lock may be in a locking position, and thereby provide a "locked" output from the sensor even when the door is not in the closed position. Alternative arrangements have relied on sensors responsive to the position of the door itself but these do not indicate whether the lock is correctly engaged. Previous arrangements may provide a "locked" output even when a part of the mechanism is damaged and incapable of restraining the door.

There are also other mechanisms where it is necessary to lock a member in position and indicate correct locking.

It is an object of the present invention to provide alternative restraining mechanisms.

According to one aspect of the present invention there is provided a restraining mechanism for restraining a first member in a defined position, the restraining mechanism including a restraining member having a restraining portion and a stop in the region of the restraining portion, the restraining member being movable between a first position in which the restraining portion engages the first member and a second position where the first member is unrestrained by the restraining portion, and the mechanism including a follower member mounted with the restraining member, means urging the follower member relative to the restraining member against the stop and sensor means responsive to the position of the follower member.

The restraining member is preferably movable between the first and second positions by rotation about a first axis. The follower member is preferably rotatable relative to the restraining member. The follower member is preferably rotatable about the first axis. The restraining portion may be a hook member. The sensor means may include a microswitch.

According to another aspect of the present invention there is provided an assembly including a restraining mechanism according to the above one aspect and an actuator operable to move the restraining member between the first and second positions.

According to a further aspect of the present invention there is provided a locking mechanism including a locking arm mounted at a location between its ends for rotation about an axis at right angles to its length, an actuator coupled with the locking arm towards one end and operable to rotate a hook portion towards the opposite end of the locking arm into or out of engagement with a locking pin, a follower member mounted with the locking arm and rotatable relative to the locking arm about the axis of rotation of the locking arm, a spring for urging the follower member into contact with a stop on the locking arm in the region of the hook portion such that in normal use the follower member is rotated with the locking arm but, if the locking arm should be damaged such that the stop is separated from the arm, the follower member is rotated relative to the locking arm, a sensor responsive to the position of the follower member to indicate whether the locking arm is engaged with the locking pin or not, and wherein the sensor is operable to indicate if the follower has moved relative to the locking arm when the locking arm is in a nominal locking position.

According to a fourth aspect of the present invention there is provided a locking mechanism for a thrust reverser door including a restraining mechanism, according to the above one aspect of the present invention, the first member being a locking pin mounted with the thrust reverser door, and the mechanism including an actuator operable to rotate the restraining member relative to the locking pin to lock or unlock the mechanism.

A locking mechanism for a thrust reverser door will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a simplified plan view of a gas-turbine engine thrust reverser; Figure 2 illustrates the locking mechanism with the thrust reverser door closed and locked; Figure 3 is a cross-sectional elevation view of a part of the locking mechanism along the line 111-111 in Figure 2; Figure 4 illustrates the locking mechanism with the thrust reverser door open and unlocked; Figure 5 illustrates the locking mechanism in a locked position but without the door being captured by the mechanism; and Figure 6 illustrates the locking mechanism with its locking arm damaged.

With reference first to Figure 1, the thrust reverser I is mounted at the rear end of an aircraft gas-turbine engine 2 and has two doors 3 and 4, which are normally in a closed position where they lie aligned with the external surface of the thrust reverser. The doors 3 and 4 are hinged about respective axes 5 and 6 and can be swung through a limited angle about these axes by respective actuators (not shown) to positions (shown by the broken lines) where a part of the doors projects into the gas stream at an angle so as to deflect the gas stream in a generally forward direction relative to the direction of travel of the aircraft.

In order to retain the doors 3 and 4 in the closed position until they are needed to open, the assembly 1 includes a locking mechanism 10 for each door (only that for the door 3 being shown), which is arranged to engage a locking roller or pin 7 fixed with the door.

With reference now also to Figures 2 and 3, the locking mechanism 10 includes a locking arm 11, which is movable by an actuator 12, a follower member 13 and a sensor 14 operated by the follower member. The arm 11 is a flat metal member pivoted midway along its length about an axle 12 for rotation through a limited angle about an axis at right angles both to its length and to the plane of the arm. The upper portion 15 of the arm 11 is straight and tapers slightly to a reduced width at its end 16 where it carries a short pin 17 projecting parallel with the axle 12. The pin 17 is slidable within a closed lateral slot 18 at the end of a rod 19 projecting from the actuator 12. Operation of the actuator 12 causes the rod 19 to move axially in or out relative to the actuator housing 20 and hence rotates the arm 11 about the axle 12.

The lower portion 21 of the arm 11 is shaped as a hook to form a recess 22 and a tooth 23 on the left-hand side of the arm. The dimensions and geometry of the hook portion 21 are such that when the locking pin 7 on the door 3 or 4 locates in the recess 22 in contact with its floor 24, the edge 25 of the tooth 23 projects a short distance beyond the radius of the locking pin. In this way, the locking pin 7 is securely retained against movement along its arc of travel 26. The lower portion 21 of the arm 11 is also formed with an integral stop formation 27 on its upper surface in the region of the tooth 23 to provide a stop surface 28.

The follower member 13 is mounted on the arm 11 and comprises a rigid planar metal component with a collar 30 at one end coaxially embracing and rotatable relative to the axle 12. A lever 31 projects radially outwardly from one side of the collar and the far end of this is engaged by one end 33 of a helical spring 32. The other end 34 of the spring 32 is secured to a fixed structure 35 and the spring is held in tension such that it applies a bias torque to rotate the follower 13 clockwise. The force applied by the spring 32 is relatively small compared with the force that can be applied relative to the actuator 12 so that it does not have any significant affect on movement of the arm 11 itself. A finger 36 projects from the collar 30 diametrically opposite the lever 31. The finger 36 is triangular with a rounded apex 37. In the position shown in Figure 2, the apex 37 of the finger 36 engages the sensor 14, which is a microswitch fixedly mounted alongside the arm 11. The follower 13 also includes a leg 40 of an angled, dog-leg shape extending along the entire length of the lower portion 21 of the arm 11. The left- hand side of the lower end 41 of the leg 40 is urged by the spring 32 against the stop surface 28 on the stop 27 and, in this way, rotation of the follower 13 relative to the arm 11 is prevented in normal circumstances.

In the position shown in Figure 2 where the door roller 7 is retained and locked by the mechanism 10, the microswitch 14 provides a LOCKED output.

When it is necessary to open the doors 3 and 4, the locking mechanism actuator 12 is energised to cause the rod 19 to extend relative to the housing 20 thereby pushing the upper end 16 of the locking arm 11 to the left and rotating the lower end 21 to the right, as shown in Figure 4. The edge 25 of the tooth 23 moves to the right away from the door locking roller 7 so that it can move down along its arc of movement 26. As the locking arm 11 rotates, the follower 13 rotates with it against the action of the spring 32. This rotates the finger 36 out of engagement with the microswitch 14 so that this changes state to provide an UNLOCKED output.

These are the normal states of operation of the thrust reverser and the locking mechanism; from the output of the microswitch it is possible to confirm whether the doors are correctly locked closed or have been opened.

There are occasions, however, when faults may occur.

Figure 5 shows the locking mechanism 10 when the locking arm 11 has been displaced to the clockwise, locking position but when the door roller 7 is not in the correct position (the correct position being shown by the broken line circle). This causes a small overtravel in movement of the locking arm 11 and the follower 13 so that the finger 36 of the follower moves slightly past the microswitch 14. In this position, the microswitch 14 continues to provide an UNLOCKED output to indicate that the door 3 is not correctly locked.

Figure 6 shows the locking mechanism 10 where a lower part 40 of the locking arm 11 has broken off. This is the part that is subjected to most stress and is, therefore, most liable to be damaged. It is important to know when the locking arm has been damaged because it might be in the correct, nominally locking position and still provide a LOCKED output from a sensor although it was unable to restrain the door. The arrangement of the present invention allows damage of this kind to be detected. It can be seen that the lower part of the locking arm 11, which has been broken off, carries the stop 27 so there is now no longer anything to prevent the spring 32 rotating the follower 13 clockwise relative to the locking arm. Even though the locking arm 11 is in the correct orientation for locking, the follower 13 is displaced beyond this position so that its finger 36 does not engage the microswitch 14. The microswitch 14, therefore, provides an UNLOCKED output.

The arrangement of the present invention enables an indication of the state of the locking mechanism to be provided in a variety of situations.

It will be appreciated that the invention is not confined to apparatus for restraining thrust reverser doors but could be used to restrain a variety of different movable members.

Claims

1. A restraining mechanism for restraining a first member in a defined position, wherein the restraining mechanism includes a restraining member having a restraining portion and a stop in the region of the restraining portion, wherein the restraining member is movable between a first position in which the restraining portion engages the first member and a second position where the first member is unrestrained by the restraining portion, and wherein the mechanism includes a follower member mounted with the restraining member, means urging the follower member relative to the restraining member against the stop and sensor means responsive to the position of the follower member.

2. A restraining mechanism according to Claim 1, wherein the restraining member is movable between the first and second positions by rotation about a first axis.

3. A restraining mechanism according to Claim 1, wherein the follower member is rotatable relative to the restraining member.

4. A restraining mechanism according to Claims 2 and 3, wherein the follower member is rotatable about the first axis.

5. A restraining mechanism according to any one of the preceding claims, wherein the restraining portion is a hook member.

6. A restraining mechanism according to any one of the preceding claims, wherein the sensor means includes a microswitch.

7. A restraining mechanism substantially as hereinbefore described with reference to the accompanying drawings.

8. An assembly including a restraining mechanism according to any one of the preceding claims and an actuator operable to move the restraining mechanism between the first and second positions.

9. A locking mechanism including a locking arm mounted at a location between its ends for rotation about an axis at right angles to its length, an actuator coupled with the locking arm towards one end and operable to rotate a hook portion towards the opposite end of the locking arm into or out of engagement with a locking pin, a follower member mounted with the locking arm and rotatable relative to the locking arm about the axis of rotation of the locking arm, a spring for urging the follower member into contact with a stop on the locking arm in the region of the hook portion such that in normal use the follower member is rotated with the locking arm but, if the locking arm should be damaged such that the stop is separated from the arm, the follower member is rotated relative to the locking arm, a sensor responsive to the position of the follower member to indicate whether the locking arm is engaged with the locking pin or not, and wherein the sensor is operable to indicate if the follower has moved relative to the locking arm when the locking arm is in a nominal locking position.

10. A locking mechanism for a thrust reverser door including a restraining mechanism according to any one of Claims I to 7, wherein the first member is a locking pin mounted with the thrust reverser door, and wherein the mechanism includes an actuator operable to rotate the restraining member relative to the locking pin to lock or unlock the mechanism.

11. A locking mechanism substantially as hereinbefore described with reference to the accompanying drawings.

12. Any novel and inventive feature or combination of features as hereinbefore described.