Rotating union

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A rotary feedthrough enables fluids (gases, liquids) to seal the transition between a stationary body and a rotating body, or between bodies rotating against one another.

Construction of a simple compressed air rotary feedthrough
Structure of a 4-channel hydraulic rotary feedthrough (sectional view)

Executions

Rotary unions can be single-flow (single-channel) or multi-flow (multi-channel). A simple example of a single-flow rotating union is the garden sprinkler, in the transition to the rotating or pivoting arm. It becomes more complex when fluids, e.g. B. hydraulic fluids, must be carried back and forth under high pressure , so if you need paired rotary unions. Single-flow bushings often use axial, multi-flow primarily radial interfaces for transferring the media. A device that enables a mechanical rotary movement to be transmitted through a container wall is also referred to as a rotary feedthrough. Applications are, for example, in vacuum technology.

Applications

  • A typical application is hydraulically driven undercarriages of excavators , the drive chains of which are driven by hydraulic motors. The drive motor and hydraulic pumps are located in the rotating superstructure, to which return oil and leakage oil must be returned to the hydraulic oil tank.
  • In motor vehicles and trailers that are equipped with a tire pressure control system, the pressure in the tires is regulated with compressed air from a central pressure vessel. The rotating tires are supplied with compressed air via rotating unions while driving.
  • In machine tools with internally cooled tools is an introduction to transport the cooling lubricant into the tool spindle required. The greatest challenge is to bring the medium into the spindle without leaks at up to 120,000 revolutions per minute. In order to guarantee an optimal sealing function of the entry, it is important that the hoses are attached without tension. Multi- channel rotary unions are also used on rotary tables with hydraulic chucks .
  • In the paper industry, rotary unions with a so-called siphon are used. In order to heat the large dryer rollers, steam is introduced, condensed and then pushed out again via the siphon.
  • In the household, rotary unions are used in household fittings such as swiveling water taps and shower heads. Rotary unions are also used in lawn sprinklers.
  • Ferrofluidic rotary feedthroughs are used as vacuum seals in coating systems in which the objects to be coated are rotated over a steam source in order to achieve a uniform layer thickness, or as gas seals in the supply of purging gases during lamp manufacture.

Seals

Rotary unions can use frictional conventional elastomer seals , sealing gas seals, mechanical seal or frictionless ferrofluid seal technology be constructed.

Other names

Rotary feedthroughs are also referred to as “ hydraulic slip rings”, analogous to electrical slip rings for transmitting electricity to rotating bodies. It is often also called a rotary inlet, sealing head or steam head.

literature

  • Manfred Weck: Machine tools 2. Construction and calculation . 8th edition. Springer Verlag, Berlin / Heidelberg 2006, ISBN 978-3-540-22502-7 .
  • Dietmar Findeisen, Siegfried Helduser: Oil hydraulics. Handbook of hydraulic drives and controls . 6th edition. Springer Verlag, Berlin / Heidelberg 2015, ISBN 978-3-642-54908-3 .

See also

Web links