The actuator of the present invention comprises a cylinder with a circular cylindrical cavity slidably engaged by a stationary piston secured to the frame of the actuator by at least one rod extending through one end wall of the circular cylindrical cavity in a leak-proof manner, wherein the stationary piston divides the circular cylindrical cavity into two compartments in a leak-proof manner. Pressurizing one and venting the other of the two compartments moves the cylinder relative to the stationary piston. The outer cylindrical surface of the cylinder includes fastening device for securing an object to be linearly actuated thereto or rack engaging a pinion gear that converts the linear motion of the cylinder to a linear motion of a sliding member with another rack or to a rotary motion of the pinion gear shaft.
