An elevation device includes a mounting frame, a rotary actuator fixed to the mounting frame, a shaft connected to the rotary actuator and rotatable with respect to the mounting frame, a drive bar slidably connected to the mounting frame, and a connecting member fixed to the shaft. The shaft defines a helical groove in a lateral surface thereof. The drive bar includes a post that is movably fit in the helical groove. The mounting frame, the shaft and the drive bar constitute a conversion mechanism that converts rotation of the shaft into linear motion of the drive bar. The drive bar is slidable with respect to the mounting frame along a direction that is parallel to an axis of rotation of the shaft.