The term cylinder actuator is a broad description applied to a family of devices which convert air and fluid pressure or electrical power into useful mechanical motion. This motion, or work as it is technically termed, may be linear or rotary by nature and is used to move, lift, lower, or grasp objects via a linkage arrangement. The most common types of cylinder actuators are pneumatic, hydraulic, and electric motor driven variants. Air and oil powered actuators generally uses a piston arrangement to initiate the movement while electrical examples use a lead screw or worm gear with each type having its own specific benefits. The cylinder actuator is found in many industrial, automotive, hobby, and domestic applications and is available in a wide range of sizes and power capabilities.
The basic working principle of pneumatic and hydraulic actuator cylinders is a piston in a closed cylinder being moved by air or oil pressure. In both cases the cylinder is sealed at both ends with the actuator rod passing through a set of seals in one end cap. This creates a closed chamber above and below the piston. Pressurized fluid, typically hydraulic grade oil, or air, is introduced into either chamber to move the piston forwards or backward which, in turn, moves the actuator rod. An arrangement of valves allows the oil or air to flow into the compression chamber and out of the non-active chamber according to operator input.
The actuator rod is attached via linkages to the object it is designed to move. Rotary cylinder actuators work in the same way except the piston component is of a different design and revolves inside the cylinder rather than moving up and down. In this case, the actuator rod transfers this rotary action to a disc or plate which is attached to the work piece. In both cases, the cylinder actuator converts fluid or air pressure into useful work.
An electrically operated cylinder actuator is fitted with a motor drive which turns a nut or gear. The actuator rod in these cases has a lead screw thread or worm gear cut into its lower part which engages this gear or nut. The rotation of the gear or nut causes the actuator to move up and down the tube according to the direction in which the motor turns. The actuator rod then transfers this linear motion to the work piece in the same way as air or oil driven actuators do.
The different types of cylinder actuators each have individual characteristics which make them particularly suited to specific applications. Air-driven actuators are the most cost effective general purpose variants delivering a good balance of power to cylinder size. They are also useful where electrical power is not readily available. Hydraulic actuators are the most powerful of all the types, delivering extreme levels of torque in any given cylinder size. Electric actuators are the most accurate types capable of delivering their motion in very precise increments.
The cylinder actuator is a common component of construction and earth moving machinery, and industrial and automotive equipment, and is an integral part of many hobby projects. They are also often encountered in the home in the form of door, skylight, and window openers. The cylinder actuator comes in a wide range of sizes and power ratings ranging from hobbyist mini-cylinders less than half an inch in diameter to giant industrial versions several feet in diameter capable of moving tens of thousands of pounds.