Hydraulic and Pneumatic Cylinder Parts
Section 1

A hydraulic cylinder and a pneumatic cylinder have the same basic parts. They each have a cylinder body, two covers, a piston, piston rod and packing gland with packing or seals. With a single-acting hydraulic or pneumatic cylinder, a spring may also be included. If it is cushioned, some type of cushion assembly is also needed.

Hydraulic and Pneumatic Cylinder Bodies

The body of a cylinder can be made from many types of materials. The body of the pneumatic cylinder we make for belly (bottom) dump trailers is constructed from a composite material that is incredible strong yet lightweight. However, a hydraulic or pneumatic cylinder can also be manufactured from cast iron, bronze, steel, aluminum or other materials. Often, when the body is of cast construction, one cover is cast integral with the body. On rotating cylinders, the rod-end cover is often cast integral with the body but on nonrotating cylinders, the blind cover is usually the one that is cast integral. The inside surface of the body must be very smooth so that it does not wear the packing and seals. A body for heavy-duty, mill-type hydraulic cylinders often has heavy steel rings on each end. These rings contain the holes for mounting the the covers on the body.

Hydraulic and Pneumatic Cylinder Covers

The terminology for covers on a hydraulic or pneumatic cylinder is somewhat confusing. The rod end, front cover and stem end all mean the cover through which the piston rod moves. This is the cover that houses the rod bearing and, on double-acting cylinders, carries the rod packing and seals. The cover that is opposite from the piston rod is called the blind end or back cover. Unless there is a cushion, there will not be packing and bearings in this end.

Covers are made from many materials including die cast aluminum, cast aluminum, cast steel, plate steel, cast iron and cast bronze. The rod end bearings are usually made from bronze or cast iron. Long-stroke cylinders often need extra long bearings.

Hydraulic and pneumatic cylinder covers come in all kinds of shapes and sizes. They can be round, square or a special shape to fit the body. The covers are held onto the body by many methods including screws, tie rods, threaded connection and metal inserts. There also are a number of ways cylinders are mounted to whatever stationary device they are attached to. For nonrotating cylinders, these mountings can include clevis, trunnion, foot, rabbeted, flange on rod end and flange on blind end. Sometimes a combination is used, such as rabbeted-mounted on the rod end with flange-mounted on the blind end.

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cylinder please call
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