To avoid chattering when using a spool in a hydraulic valve, it is often necessary to hold the spool in a locked position until the external force exceeds a certain threshold value. In this example of a spool with a preload, we will explore the interaction between such a force and the spool's position.

System Architecture

The system is a standard example in the Modelica.Mechanics.Translation library showing an example of usage of the ElastoGap component (the outer and inner contacts in the model). The ElastoGap component is essentially a spring-damper component with a gap, meaning that the spring damper will only be used if the gap is closed. This behavior simulates the desired preload to the spool.

A force is generated from a source and applied to the spool. When the spool has moved a threshold distance, which has the effect of loading a force in a spring, the gap is closed in the Contact components and the spool will begin to move.

Further Investigation

In the accompanying notebook, the behavior of this system is animated and can be interacted with.

In order to get the full experience of this example, you need a desktop Wolfram Language product. A free trial download is available at www.wolfram.com/mathematica/trial/

For the full example, open the accompanying notebook SpoolWithAPreLoad.nb.