Bellows for Screw Jacks

1. Function and application of Bellows

Folding Bellows are used to protect screw systems from external influences such as dust, moisture, and other contaminants. They play a key role in ensuring the service life and reliability of Screw Jacks.

Typically, Bellows can easily cover:

1. screw lengths from 10 mm to 4.000 mm
2. screw diameters from Ø10 mm to Ø250 mm

2. The “breathing” Bellows – Why pressure equalization is necessary

One often overlooked aspect is the behavior of the Bellows during operation:

1. When extending, a vacuum is created
2. When retracting, positive pressure is created

In other words, the Bellows “breathe.” Without proper pressure equalization, this can lead to malfunctions or premature wear.

3. Standard solution: Pressure equalization via vent filters

The most common solution for pressure equalization is the use of vent filters. These allow air to flow in and out while simultaneously filtering larger particles from the incoming air.

Advantages:

✅ Simple and cost-effective solution

✅ Sufficient for many standard applications

4. Problem case: Fine contamination

If the contaminants in the environment are very fine, they can pass through the vent filter and enter the system. Since the Bellows tends to trap these particles, this can actually accelerate wear.

In heavily contaminated or fine dust environments, an alternative solution is therefore required.

5. Innovative solution: Pressure equalization hose

For such cases, a pressure equalization hose can be used. It transfers air back and forth between the Bellows and the protective tube, or between two Bellows.

Advantages:

✅ No contact with ambient air

✅ No ingress of contaminants

✅ Significantly reduced wear

This solution is not only technically superior but also economically attractive—so much so that some users are consistently converting their systems to it.

6. Alternative protection systems for screws

In addition to bellows, other protection solutions are available:

1. spiral protective sleeves
2. enclosures / telescopic covers

These are typically provided by the customer. The choice of the appropriate screw protection system depends on the available installation space and the level of contamination in the operating environment.

7. When Bellows are not suitable

There are also applications in which the use of Bellows is not recommended. For example, when there is insufficient installation space for Bellows and the operating environment is very clean. In such cases, Bellows can be omitted.

8. Conclusion

Bellows are a proven and flexible solution for protecting Screw Jacks. However, their performance depends heavily on a correct assessment of the operating environment. While vent filters are sufficient for many applications, closed systems with a pressure equalization hose offer clear advantages in demanding environments. The appropriate protection system should therefore always be selected based on the specific operating conditions.