Variable force spring that does not restricted to Hook's Law for compression springs that the load increases proportionally with stroke. According to your request, you can have a multi-load design. Here are some relations between load and stroke that can be used on specific occasion. The product range from 0.03~0.75mm in thickness and 1~50mm in width.

There are large selections of various springs for brush holders. The advantage of constant force spring for carbon brush are as following: Constant pressure for commutator in any brush length. Increases brush life, reduces electrical wear. Compact design for smaller motor overall diameter that allows longer brushes and larger commutators, featuring reduced spark, lower influence of electromagnetic interference(EMI). The product range from 0.03~0.75mm in thickness and 1~50mm in width.