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Magnetically Coupled Cylinders


Magnetically Coupled Cylinders; cylinders designed to fill a specific need!

Unlike other types of rodless cylinders, such as a band cylinder or a cable cylinder, there is no mechanical connection between the carriage and the piston inside the cylinder barrel on a magnetically coupled air cylinder.

Instead, inside the cylinder, a strong rare-earth magnet will be part of the cylinder piston, and, another similar magnet will be part of the cylinder carriage. The attraction between these two magnets is what allows the carriage to be moved along outside cylinder barrel by the piston, which is being propelled along inside the cylinder barrel by compressed air.





In the drawing above we focus on the piston inside the cylinder barrel, conceptualizing the magnet built in as part of the piston assembly.

Each manufacturer of magnetically coupled air cylinders will have their own design, of course.

The sketch below shows the carriage on the cylinder to the left, and then an end view of the carriage, with the magnet as part of the carriage itself.





Depending on the manufacturer, there may be a single magnet on the piston and in the carriage, or multiple magnets, unique to their design.

All magnetically coupled air cylinders are not the same. It is necessary to select the cylinder that provides the “coupling force” between the carriage and piston that suits the load and the speed of what is to be moved.

Mounting styles of the magnetically coupled cylinders vary too. The simplest is the cylinder with a threaded tang on each end. These tangs fit through a hole in the boss, and then a jam nut is threaded on clamping the cylinder in place.

Different styles offer variations on plumbing, with air ports in the end or on the sides of the end caps.


Benefits of the magnetically coupled design

  • Magnetically coupled cylinders are normally leak proof, making them ideal to use in areas where compressed are leaks would be a problem
  • Most can be used for low pressure hydraulic service, again, because they don’t leak
  • In the event that the carriage and piston magnets “uncouple”, simply moving the carriage to where the piston is allows them to magnetically “reconnect”


    Negatives of the magnetically coupled design

  • High speed carriage movement combined with rapid or hard deceleration can “uncouple” the carriage from the piston
  • The carriages on this type of cylinder have no mechanical connection to the cylinder itself, therefore, an external load and carriage guidance system is almost always required
  • These types of cylinders tend to be high cost solutions over other rodless cylinders


  • What are some of the things you need to know to select the appropriate magnetically coupled air cylinder?

  • What is the weight and size of the load you wish to move
  • How will the carriage be supported
  • What is the distance the load will be moved
  • What is the speed required in distance per second
  • What will stop the load / carriage at the end of stroke
  • Is position sensing required
  • How will the cylinder be mounted






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