Saturday, October 1, 2011
Hydraulic Cylinders
A hydraulic cylinder is a mechanical device for transferring power through the utilization of high pressure oil acting against the surface area of an piston within the cylinder. A hydraulic cylinder provides linear force in one axis in either one or two directions (known as a single or double acting cylinder respectively). The cylinder is typically made up of 4 or 5 components: - Tube - Piston (optional) - Rod - Gland - End cap In a typical hydraulic cylinder having a piston oil is fed in at either end via some kind of 'port' and the piston is sealed towards the tube by a double acting seal and also between the rod and also the gland by a single acting seal. In addition, you will usually find a wiper seal is utilized inside gland to keep dirt out. This illustration is known like a double acting cylinder. It is the pressure acting upon the piston surface which causes a the hydraulic cylinder to produce a linear movement. Because the rod is fixed for the piston, it moves too. Application of hydraulic pressure through the port to one side in the piston causes it to move in one direction, and application of pressure through the port to the opposite side from the piston will cause it to move inside the opposite direction. In a single acting cylinder, oil only acts on one side from the piston so it could only be mechanically moved in one direction. An external force (gravity, or sometimes a spring or another hydraulic cylinder) provides force in the opposite direction. Single acting cylinders can be also of the "displacement" type where the oil pressure acts directly about the end of the rod, and there is no piston. Within this cylinder design the force is limited through the surface area from the rod, whereas in a cylinder having a piston, the rod can be of any size and also the force can be calculated or controlled through the piston design. Typically one end of the tube is fixed and on the end from the rod is attached the object to become moved, although it's possible to fix the end from the rod, and attach the object being moved on the end of the tube. In a double acting cylinder the "closing" power is always less compared to "opening" power due to a reduced surface area of the piston for the oil to act upon. This reduced surface area is exactly the surface area in the end in the rod. The height and width of a hydraulic cylinder can be virtually limitless, typically from the few centimeters in length to several meters, although in theory you can find few limitations.
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