Machine Design

Magnets replace gas in springs

Gas springs use high-pressure gases, hydraulic fluid, or air to push or pull a rod within a cylinder.

Unfortunately, they also leak, risk exploding or contaminating the environment, and change the amount of force they exert due to temperature fluctuations. A new approach, Magna-Lift magnetic springs from Magna Motor Inc., Chippewa Falls, Wis., sidesteps these problems by using magnets to supply the pushing or pulling forces. They operate in temperatures ranging from 200 to 430F, with no demagnification or loss of internal forces. They are also self-contained, needing no electrical or hydraulic connections. The springs use a series of neodymium ring or disk magnets inside a cylindrical enclosure.

For a spring that closes or retracts the rod, magnets are configured to repel each other, with one magnet's north pole facing the next magnet's north pole. Pulling the rod out, either manually or mechanically, pushed the magnets together. Once the rod is released and free to move, the magnets repel each other, retracting the rod into the cylinder. When this device is used to close doors, a backlash damper spring and an auto-release locking system can be added.

For a magnetic spring that pushes the rod out of the cylinder, magnets are again arranged to repel each other. As the rod is pushed into the cylinder, the magnets are pushed together, generating repulsive forces that are unleashed when the rod is free to move and pushing the rod out of the cylinder.

Spring forces can be adjusted by using different grade, sizes, or quantities of magnets. The springs can be housed in a variety of nonmagnetic materials and be suitable for light or heavy-duty service. Piston rods can be stainless steel, aluminum, brass, carbon fiber, or finer glass. There are no internal parts or seals to wear out, providing almost unlimited shelf life and years of maintenance-free operation.

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