Stent delivery device

A stent delivery device comprising:

• a shaft comprising an internal lumen, the shaft extending in an axial direction;
• a balloon connected the shaft, the balloon being inflatable radially outward and deflatable radially inward between a deflated state and an inflated state;
• a cover configured to advance or retract in the axial direction of the shaft between a covering position where the cover covers the balloon when the balloon is in the deflated state and a retracted position where the cover is axially spaced apart from the balloon;
• a drive unit configured to apply a driving force for advancing or retracting the cover in the axial direction;
• the lumen of the shaft being configured to allow a working fluid injected into the lumen of the shaft to flow into the balloon to inflate the balloon, the working fluid being dischargeable from the lumen of the shaft, the balloon and drive unit being operated by the injecting and discharging of the working fluid;
• and
• the inflating and deflating of the balloon and the advancing and retracting of the cover being performed in conjunction with each other, wherein
• the drive unit has a piston connected to the cover and a housing portion configured to house the piston so that the piston is slidable within the housing portion relative to the housing portion, and
• the drive unit comprises a piston rod that extends into the housing portion, the piston rod being moveable to abut the piston to restrict the piston from sliding within the housing portion and retractable from the piston to release the sliding restriction on the piston.