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Basic Design
While rotating joints come in many shapes, sizes, and
configurations, they always have the same four basic components: a housing, a
shaft, a bearing (or bearings) and a seal.
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| The heart of the rotating joint is the seal.
The seal is the element that prevents the medium from leaking outside the joint
while the joint is in operation. DuffNorton uses four basic
types of mechanical seals in its Rotary Unions°: pusher-type
end face mechanical seals, non-pusher type end face mechanical seals,
lip seals, and o-ring seals. Joints may have more than one seal. The second
most important part of the rotating joint is the bearing. A
Rotary Union may have only one bearing or multiple bearings. Roller
bearings (like ball bearings and tapered roller bearings) or nonroller
bearings (like graphite bearings and bronze 4ushings) may be used
in the Rotary Union. The "bearings are, always used to allow a part of the
joint (either the shaft or the housing) to rotate. |
The shaft is the component that
carries the medium through the joint into the drum or roll. In many cases, the
shaft will turn with the drum or roll. In some cases, like in larger, flanged
joints, the shaft may be stationary while the housing rotates. The bearings and
seal are typically assembled around the shaft. The housing is the component
that holds all of the other elements of the joint together. The housing
has an inlet port, which is a threaded hole to which the hose supplying the
medium will be attached. It may also have an outlet port, if the same joint is
being used both to supply fluid to a roll and to remove fluid from the roll. In
smaller joints, the housing is stationary. In larger joints, the housing maybe
bolted (using a flange) to the drum or roll. In these cases, the housing
rotates at the same speed as the drum.
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