Patent ID: 8593568

Claim:
A shape memory alloy actuation apparatus comprising: a support structure; a movable element; a suspension system comprising a plurality of resilient flexures coupled between the support structure and the movable element to support the movable element on the support structure and to guide movement of the movable element along a movement axis by deflection of the flexures; a shape memory alloy actuator arranged to drive movement of the movable element relative to the support structure in a first direction along the movement axis, on contraction of the shape memory alloy actuator; an end-stop arranged to limit the movement of the movable element in a second direction along the movement axis, opposite to the first direction; a biassing element comprising a resilient flexure arranged to bias the movable element relative to the support structure in the second direction along the movement axis, the apparatus being arranged such that, when the moveable element is held against the end-stop, the force applied by the biassing element in said second direction is greater than the force applied by the flexures of the suspension system, the length of the resilient flexure of the biassing element, as measured between positions at which it is coupled to the support structure and the movable element, being greater than that of the plurality of resilient flexures of the suspension system.