GB1575252A - Latch assembly - Google Patents

Description

(54) AN IMPROVED LATCH ASSEMBLY (71) We, AIRCRAFT MATERIALS LIMITED, of Midland Road, -London NW1 2AB, a 'British Company, do hereby -declare the invention, for which we pray that -a patent may be granted.to :iis, and - the method by which it is to be performed, to be particu larly described in .and by the following -statement:- This invention has for its objectto provide a latch assembly for securing a door - or access panel in position-to close an aperture in the external surface of an aircraft.Such - an assembly must be highly safe in operation, provide no projection from the surface to which it is attached and be capable of retaining the door or panel firmly closed not withstanding subjection to aerodynamic loads.

The latch assembly according to the invention comprises a channel, a bolt dis posed within and extending lengthwise of the channel, a spring urging the bolt to a locking position in which it is -projected from the channel, an operating handle which is pivoted to the channel and normally occupies a flush position in which it is inaccessible for grasping by an operator, means operable by pivotal movement of the handle to retract the bolt to a free position, and a trigger on the handle which is movable to two alterna tive control positions, in one of which it -retains the handle in the flush position and in the other of which it permits of automatic limited pivotal movement of the handle to a preliminary position in which it .can be grasped, and also to a freeing position in which it permits the handle to be rotated manually beyond the preliminary position to retract the bolt.

In operation it is necessary to operate the .trigger twice, firstly to cause the handle to move to the preliminary position and then again to free the handle for further movement -to retract the bolt. This constitutes a safety .device to ensure that the door or panel to which the latch assembly is fitted cannot be opened in response to inadvertent actuation of the trigger. The spring constitutes a further safety element since it ensures that the bolt will be loaded to the projected position while the handle is being rotated to retract 'the bolt.

One embodiment of the invention is -illustrated, -by way of example, in the ac companying drawings, in which: Fig. 1-is a side.view of the' latch; Fig. 2 is a plan.view; Figs. 3-5 are longitudinal sections-show ing the latch in three different positions7 Fig. 6 is an view on a larger scale of the central-portion of Fig. 3; Fig..7 is a section on the line VII-VII in Fig. 6; and Fig. 8 is a -section on the line VITI-VIII in Fig. 6.

The latch includes a channel 1, within which is a longitudinally disposed bolt 14, which is slidable in a bush 16 and is urged'by a spring 12 to the projected position shown in Fig. 1 in which it locks a door or panel A, to which the latch is fitted, to an adjoining structure B. The rear end of the.bolt 14 constitutes a socket 20 surrounding.a:head 21 (Fig.-6) on the forward end of a rack 7 which extends longitudinally within the channel 1. A pin 18 attached to -the rack engages with lost motion slots 22 in the socket 20.

A channel section handle 2 is pivoted to the channel by a pin 24. A lever 6, pivoted to the channel by a pin 25 is urged by a spring 13 into contact with a stop 26 on the handle2 and so tends to lift the handle 2 from the flush position shown in Fig. 6. The handle 2 is, however, normally retained in this position by a trigger 5, which is pivoted to the handle by a pin 27 and urged by a spring 28 into the position shown in which its upper hook 29 engages pins 30.which project inwardly,from the- side walls of the channel 1, as shown in Fig. 7. In this locked position a nose.31 on the lever 6 lies opposite the pin 18 to preclude any significant movement of the bolt. l4 towards the free position under the action of aerodynamic loads.

To retract the bolt 14, the trigger 5 is depressed causing the pins 30 to engage its lower hook 32. Pins 40 on the channel coact with the right hand face of the trigger, as seen in Fig. 3, to ensure engagement of the hook by the pins 30. This enables the spring 13 to rock - the lever 6 and cause the handle 2 to move anticlockwise through 9" to a position shown in Fig. 4 in which it can be grasped by the hand. A toothed segment 3, carried by the handle 2 meshes with another segment 4 rotatably mounted in the channel and meshing with the rack 7. The initial small movement of the handle 2 causes the rack 7 to move to the left within the limits of the lost motion provided by the slots 22. Further movement of the handle at this stage is prevented by engagement of the pins 30 with the hook 32.

Further depression of the trigger 5, however, frees the hook 32 from the pins 30 and enables the handle 2 to be rotated manually through a further 90" to the position shown in Fig. 5, so causing the rack 7 to retract the bolt 14, against the action of the spring 12, to a position in which it is locked by engagement of a recess 33 in the lever 6 with a pin 19 on the bolt 14.

To project the bolt again, the handle 2 is pressed to overcome the spring load on the lever 6 and free the pin 19, so allowing the spring 12 to become effective. The handle 2 may then be moved back to the flush position shown in Fig. 3.

With the exception of loads imposed by inserting the bolt when misalignment occurs between the bolt and its co-operating hole in the other structure, all loads are transmitted through the mechanical lock engaging the transverse pins 18 and 19 by-passing all other elements of the mechanism.

Safety features are as follows The bolt 14, when projected, is mechanically locked against linear movement in both directions performing the same function and eliminating the need for an "over centre" toggle. The handle 2 and the trigger 5 are spring latched to the channel 1 whilst the bolt 14, in addition to being mechanically locked, is spring loaded towards the projected position.

The handle 2 is held against further aerodynamic opening loads when opened to 90 as shown in Fig. 4 and within such movement the bolt 14 is mechanically locked and spring loaded towards the projected position, with the handle and the trigger spring latched to the channel.

On second depression of the trigger 5 the handle 2 can be rotated through 90" whilst the bolt 14 is spring loaded towards the projected position.

The handle after rotation through 90" from the 9" position (during which movement, as stated above, the bolt is spring loaded towards the projected position) is locked by pressure from the spring loaded lever 6 to the handle. When in fully open position the bolt will be nominally .012" inside the bush 16.

As an alternative, the slots 22 may be on the rack 7 and the pin 18 on the bolt 14.

In this case, to prevent chatter through the gears to the handle, a rubber plug may be fitted into a hole in the bolt and abut the right hand face of the head 21.

As will be appreciated, the latch assembly can be varied in geometry to suit the location on the aircraft at which it is to be fitted.

WHAT WE CLAIM IS:- 1. A latch assembly, for securing a door or access panel in position to close an aperture in the external surface of an aircraft, comprising a channel, a bolt disposed within and extending lengthwise of the channel, a spring urging the bolt to a locking position in which it is projected from the channel, an operating handle which is pivoted to the channel and normally occupies a flush position in which it is inaccessible for grasping by an operator, means operable by pivotal movement of the handle to retract the bolt to a free position, and a trigger on the handle which is movable to two alternative control positions, in one of which it retains the handle in the flush position and in the other of which it permits of automatic limited pivotal movement of the handle to a preliminary position in which it can be grasped, and also to a freeing position in which it permits the handle to be rotated manually beyond the preliminary position to retract the bolt.

2. A latch assembly according to claim 1, which includes a lever pivoted to the handle and spring urged in the direction to move the handle from its flush position, the lever coacting with alternative pins on the bolt so as respectively to prevent it from retraction from its projected position under the action of aerodynamic loads and to retain it in its retracted position.

3. A latch assembly according to claim 1 or claim 2, in which the trigger carries two hooks which co-operate with a pin on the channel to retain the handle in the flush position and in the preliminary position respectively.

4. A latch assembly according to any one of the preceding claims, in which the handle carries a toothed segment which is operable on pivotal movement of the handle to impart movement to a rack attached to the bolt.

5. A latch assembly according to claim 4,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. lower hook 32. Pins 40 on the channel coact with the right hand face of the trigger, as seen in Fig. 3, to ensure engagement of the hook by the pins 30. This enables the spring 13 to rock - the lever 6 and cause the handle 2 to move anticlockwise through 9" to a position shown in Fig. 4 in which it can be grasped by the hand. A toothed segment 3, carried by the handle 2 meshes with another segment 4 rotatably mounted in the channel and meshing with the rack 7. The initial small movement of the handle 2 causes the rack 7 to move to the left within the limits of the lost motion provided by the slots 22. Further movement of the handle at this stage is prevented by engagement of the pins 30 with the hook 32. Further depression of the trigger 5, however, frees the hook 32 from the pins 30 and enables the handle 2 to be rotated manually through a further 90" to the position shown in Fig. 5, so causing the rack 7 to retract the bolt 14, against the action of the spring 12, to a position in which it is locked by engagement of a recess 33 in the lever 6 with a pin 19 on the bolt 14. To project the bolt again, the handle 2 is pressed to overcome the spring load on the lever 6 and free the pin 19, so allowing the spring 12 to become effective. The handle 2 may then be moved back to the flush position shown in Fig. 3. With the exception of loads imposed by inserting the bolt when misalignment occurs between the bolt and its co-operating hole in the other structure, all loads are transmitted through the mechanical lock engaging the transverse pins 18 and 19 by-passing all other elements of the mechanism. Safety features are as follows The bolt 14, when projected, is mechanically locked against linear movement in both directions performing the same function and eliminating the need for an "over centre" toggle. The handle 2 and the trigger 5 are spring latched to the channel 1 whilst the bolt 14, in addition to being mechanically locked, is spring loaded towards the projected position. The handle 2 is held against further aerodynamic opening loads when opened to 90 as shown in Fig. 4 and within such movement the bolt 14 is mechanically locked and spring loaded towards the projected position, with the handle and the trigger spring latched to the channel. On second depression of the trigger 5 the handle 2 can be rotated through 90" whilst the bolt 14 is spring loaded towards the projected position. The handle after rotation through 90" from the 9" position (during which movement, as stated above, the bolt is spring loaded towards the projected position) is locked by pressure from the spring loaded lever 6 to the handle. When in fully open position the bolt will be nominally .012" inside the bush 16. As an alternative, the slots 22 may be on the rack 7 and the pin 18 on the bolt 14. In this case, to prevent chatter through the gears to the handle, a rubber plug may be fitted into a hole in the bolt and abut the right hand face of the head 21. As will be appreciated, the latch assembly can be varied in geometry to suit the location on the aircraft at which it is to be fitted. WHAT WE CLAIM IS:-

1. A latch assembly, for securing a door or access panel in position to close an aperture in the external surface of an aircraft, comprising a channel, a bolt disposed within and extending lengthwise of the channel, a spring urging the bolt to a locking position in which it is projected from the channel, an operating handle which is pivoted to the channel and normally occupies a flush position in which it is inaccessible for grasping by an operator, means operable by pivotal movement of the handle to retract the bolt to a free position, and a trigger on the handle which is movable to two alternative control positions, in one of which it retains the handle in the flush position and in the other of which it permits of automatic limited pivotal movement of the handle to a preliminary position in which it can be grasped, and also to a freeing position in which it permits the handle to be rotated manually beyond the preliminary position to retract the bolt.

2. A latch assembly according to claim 1, which includes a lever pivoted to the handle and spring urged in the direction to move the handle from its flush position, the lever coacting with alternative pins on the bolt so as respectively to prevent it from retraction from its projected position under the action of aerodynamic loads and to retain it in its retracted position.

3. A latch assembly according to claim 1 or claim 2, in which the trigger carries two hooks which co-operate with a pin on the channel to retain the handle in the flush position and in the preliminary position respectively.

4. A latch assembly according to any one of the preceding claims, in which the handle carries a toothed segment which is operable on pivotal movement of the handle to impart movement to a rack attached to the bolt.

5. A latch assembly according to claim 4,

which includes a lost motion connection between the rack and the bolt.

6. A latch assembly according to claim 1, substantially as described herein with reference to the accompanying drawings.