FOREIGN PRIORITY

This application claims priority to European Patent Application No. 17461563.3 filed Jun. 29, 2017, the entire contents of which is incorporated herein by reference.

FIELD

The present disclosure relates generally to an indicator for a torque limiter, and more specifically an indicator in the form of an elongated plug that replaces the previously used indicator arm in such applications.

BACKGROUND

Torque limiters are known in the art and comprise an input shaft and an output shaft, wherein torque is transferred from the input shaft to the output shaft in use. One or more coupling members may be provided to transmit torque from the input shaft to the output shaft. A number of systems are known in the art for preventing the overload of the coupling between the input shaft and the output shaft, which is the aim of the torque limiter. These typically work by employing a brake that is activated once a predetermined torque limit is exceeded. This method of limiting torque is typically used in aircraft applications, for example when actuating an aircraft flight control surface, in order to protect the actuator from damage.

It is known to provide a device that indicates when a torque limiting device has been activated, or tripped during flight.FIG. 1shows an example of an indication device in the form of a rotating arm.

As can be seen inFIG. 1, a torque limiter10is shown that comprises an indicator sleeve12operatively connected to one or more coupling members of the torque limiter. As is known in the art, the coupling members are typically configured to brake the input shaft and/or the output shaft upon a torque from the input shaft exceeding a predetermined amount. Various methods of braking are known in the art. For example, in some arrangements a rotating component may be linked to the input or output shaft. Upon the input torque exceeding a predetermined amount, the rotating component may cause a cam surface to begin to rotate and contact a stationary outer ring, which locks the rotating component and, in turn, the input shaft. Other arrangements are also possible, and so the specific structure of the torque limiter10will not be described herein in detail.

In order to provide the indication that the torque limiter10has tripped, upon braking the coupling members initiate a mechanical movement that moves the indicator sleeve12in the direction of arrow14. A small plunger16is located in a passageway18between the internal components of the torque limiter10(e.g., indicator sleeve12) and an external cavity20provided on the outer surface151of the housing11of the torque limiter10. Upon mechanical movement of the coupling members as aforesaid, the indicator sleeve12pushes the plunger16in the general direction of arrow14.

An indicator arm30is provided within the cavity20and is rotatable about a pivot22, such that upon movement of the indicator sleeve12and plunger16in the direction of arrow14the indicator arm30rotates in the direction of arrow24, which lifts the indicator arm out of the cavity20in the direction of arrow32.

Upon inspecting the torque limiter10, an operator may easily see the indicator arm30is raised, and will know immediately that the torque limiter has tripped.

FIG. 2shows the housing11of the torque limiter10in isolation and perspective view, from which it can be seen that the cavity20extends out from the periphery of the upper portion of the torque limiter10, and requires complex machinery, such as apertures23for accommodating the pivot22(seeFIG. 1).

It is desired to provide an improved method of indicating that a torque limiter has tripped, including an apparatus for doing so.

SUMMARY

In accordance with an aspect of the disclosure, there is provided an indicator for a torque limiter, comprising one or more members (e.g., resilient members) configured to move from an initial, compressed state (e.g., during normal operation of the torque limiter), to a subsequent, expanded state (e.g., upon tripping of the torque limiter), to provide a visual indication that the torque limiter has tripped.

The subsequent, expanded state may correspond to a rest state of the one or more resilient members, and/or the initial, compressed state may corresponds to a state in which an external force is applied in use to compress the one or more resilient members.

Upon release of the external force the one or more resilient members may be configured to move from the initial, compressed state to the subsequent, expanded state, for example to provide the visual indication that the torque limiter has tripped.

The one or more resilient members may comprise one or more resilient tines.

The one or more resilient members may be connected at a first end to an outer surface of the indicator, such that the one or more resilient members are compressible against or towards the outer surface of the indicator, and move from the compressed state to the expanded state in use by rotating about the connection at the first end.

The one or more resilient members (e.g., tines) may define an angle with respect to the outer surface of the indicator, wherein in the initial, compressed state the angle is relatively small, and in the subsequent, expanded state the angle is relatively large.

The angle may be between the outer surface of the indicator and a longitudinal axis and/or surface of the one or more resilient members (e.g., tines).

The surface of the one or more resilient members may correspond to a surface of the resilient member that is compressible towards the outer surface of the indicator.

The one or more resilient members may comprise a first set of resilient members located at a first position on the indicator, and a second set of resilient members located at a second, different position on the indicator. In use, the first set of resilient members at the first position may be configured to move from the initial, compressed state to the subsequent, expanded state prior to the second set of resilient members at the second, different position.

In accordance with an aspect of the disclosure, there is provided a torque limiter, the torque limiter comprising a cavity for retaining an indicator as described above. The cavity may extend from an outer surface of the torque limiter to an internal chamber of the torque limiter, and may be sized such that the one or more resilient members are compressed into their initial, compressed state when the indicator is located in the cavity in use.

The torque limiter may further comprise an indicator as described above and located within the cavity.

The torque limiter may further comprise a movable component configured to move in a given direction if the torque experienced by the torque limiter in use exceeds a given or predetermined amount. The movable component may be arranged to contact the indicator such that the movement of the movable component pushes the indicator at least partially through the cavity, and at least some of the resilient members completely through the cavity, such that the resilient members that are pushed completely through the cavity move from the initial, compressed state within the cavity to the subsequent, expanded state outside of the cavity and provide the visual indication that the torque limiter has tripped.

The indicator may be elongated and comprise a longitudinal axis. For example, the indicator may have a length (e.g., along its longitudinal axis) that is at least 2, 3, 4, 5 or even 10 times its largest width (e.g., laterally or transverse to its longitudinal axis). This can allow the indicator to sit inside a pocket or cavity (e.g., a cavity as described above) of relatively small dimensions, and reduce the exposure of the inside of the torque limiter to the external environment. For example, the width of the cavity may be less than 2 cm, 1 cm or even 0.5 mm.

A first set of the resilient members may be located at a first axial position along the length of the indicator, and a second set of the resilient members may be located at a second axial position along the length of the indicator. The first axial position may be closer to an end of the indicator that is located towards the outer surface of the torque limiter in use.

The movable component may be configured to push the indicator a limited amount such that, when the movable component pushes the indicator the first set of members are pushed out of the cavity and move from the initial, compressed state to the subsequent, expanded state (to provide the visual indication that the torque limiter has tripped), and the second set of members remain within the cavity and press against the surface of the cavity (to resist further movement of the indicator within the cavity). In this manner, the resilient members can provide a dual function, of firstly providing a visual indication that the torque limiter has tripped, and secondly resisting further movement of the indicator within the cavity.

The torque limiter may further comprise: a rotational input drive member; a rotational output drive member co-axial with said input drive member; one or more coupling members through which torque is transmitted from the input drive member to the output drive member; and a braking device attached to said input drive member or said output drive member and configured to restrict or prevent rotational movement of the torque limiter if the torque applied by said input drive member exceeds a given or predetermined amount; wherein said braking device comprises the movable component.

In accordance with an aspect of the disclosure, there is provided a method of installing an indicator in a torque limiter. The indicator may be an indicator in accordance with any of the aspects and embodiments described above and herein, and the torque limiter may be a torque limiter in accordance with any of the aspects and embodiments described above and herein. The method may comprise pushing the indicator into the cavity in the torque limiter such that the resilient members press against the surface of the cavity to hold the indicator in place within the cavity. The step of pushing the indicator into the cavity may be in response to the indicator being pushed out of the cavity due to the torque limiter tripping in use.

