| 摘要 |
A piston for a linear spool valve, the valve comprising a body having a inner surface. The body is made of a material with a relatively low heat expansion coefficient α1. The piston comprises a contact member having an outer surface and being adapted to reciprocate within the body of the valve so that the outer surface is in contact with the inner surface. The contact member has at least a first layer made of a material with a heat expansion coefficient α2 essentially greater than α1, i.e. α2>>α1, and at least a second layer made of a material with a heat expansion coefficient α3 close to α1. This causes the contact member to be adapted to behave, along said outer surface, as a material having a heat expansion coefficient essentially closer to α1 than to α2. One of the layers constitutes an outer layer of the contact member and comprises the outer surface.
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