Torque limiter having over-speed protection

Abstract

An apparatus for connecting a rotational drive member to a rotational driven member brakes rotation when either the torque transmitted between the members exceeds a predetermined torque limit or the rotational speed of the drive member exceeds a predetermined rotational speed limit. The apparatus includes a torque limiter configured to actuate a braking mechanism or disconnect transmission when the torque limit is exceeded, and an over-speed governor configured to trigger the torque limiter when the rotational speed of the input element exceeds the rotational speed limit. The over-speed governor may trigger the torque limiter by reducing the torque limit of the torque limiter, or by introducing rotational drag in the apparatus to increase transmitted torque.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to torque limiters for preventing the transmission of torque from a driving element to a torque responsive element when a predetermined torque limit has been reached. More specifically, the present invention relates to a torque limiter configured to lockup when the driving element experiences a rotational over-speed condition.BACKGROUND OF THE INVENTION[0002]Torque limiters are used in aircraft flight control systems to prevent the transmission of excess torque from a drive unit when a flight control surface actuated by the drive unit becomes jammed. Flight control surfaces include, for example, a trailing edge flap on a wing.[0003]A torque limiter commonly includes an input element coupled to an output element through a braking mechanism responsive to an over-torque condition, as may be experienced when the output element is prevented from rotation due to a malfunction. In a well-known arrangement, the braking mech...

AI Technical Summary

Benefits of technology

[0007]In a first embodiment, the torque limiter includes a torque limit setting spring having a preload which defines the torque limit, and the over-speed governor acts to reduce the preload of the torque limit setting spring when the rotational speed limit is exceeded, thereby reducing the torque limit needed to trigger the torque limiter so that actuation of the torque limiter is caused by any applied torque. In the first embodiment, the over-speed governor may include a preload setting shaft engaging the torque limit setting spring, wherein the preload setting shaft is axially displaceable relative to a structural ground to set the preload of the torque limit setting spring. The over-speed governor of the first embodiment may also include at least one fly weight arranged on the input element for releasably holding the preload setting shaft in an axial setting position relative to the structural ground. The fly weight may directly engage the preload setting shaft in the manner of a sear, or it may radially confine a separate sear element for maintaining the preload setting shaft in its axial setting position. When the rotational speed of the input element exceeds the rotational speed limit, each fly weight moves radially outward by centrifugal force, thereby releasing the preload setting shaft to permit axial displacement of the preload setting shaft relative to the structural ground. The preload setting shaft is displaced by the torque limit setting spring relative to the structural ground, thereby reducing the preload. All or substantially all of the preload on the torque limit setting spring may be removed such that the over-speed governor reduces the torque limit to substantially zero torque and the torque limiter will be triggered by any transmitted torque.

Problems solved by technology

While torque limiters of the type described above are effective in preventing damage to mechanical drive components caused by over-torque, they do not provide any protection when an over-speed condition is experienced.

In the context of aircraft control systems, an over-speed condition may occur if a torque tube that transmits torque to aircraft control surfaces undergoes failure and load is suddenly removed from the output element, thereby causing the input and output elements to rotate at a dangerously high number of revolutions per minute.

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