Patent ID: 7967829

Claim:
A system, comprising: an inner tube; an outer tube at least partially surrounding the inner tube so that a medical device can be positioned between the inner and outer tubes, the inner and outer tubes being configured to be capable of being disposed within a body lumen; and an actuator configured so that, as a force is applied to the actuator, the actuator can cause relative motion between the inner and outer tubes, wherein the actuator comprises a rotatable member having a first portion with a radius that gradually increases around a circumference of the rotatable member and a second portion with a stepwise change in radius, radius being determined relative to an axis of rotation of the rotatable member, wherein a mechanical advantage of the actuator changes as the actuator moves in a proximal direction, wherein a rotatable element is coupled to the rotatable member so that, as the rotatable element rotates, the rotatable member rotates, wherein the rotatable element is an external thumb wheel; and wherein the mechanical advantage of the actuator linearly decreases as the actuator moves in the proximal direction so that the actuator provides fine and controlled proximal refraction of outer tube when the thumb wheel is initially rotated and coarse proximal retraction of outer tube when the thumb wheel is later rotated.