Patent ID: 7703475

Claim:
A piston for a linear spool valve, said valve comprising a body having an inner surface and made of a material with a low heat expansion coefficient α 1 ; said piston comprising a contact member having an outer surface, and being adapted to reciprocate within the body of said valve so that said outer surface is in contact with said inner surface; said contact member having at least a first layer made of a material with a heat expansion coefficient α 2 essentially greater than α 1 , i.e. α 2 >>α 1 , and a second layer made of a material with a heat expansion coefficient α 3 close to α 1 , i.e. α 3 ≅α 1 , one of these layers constituting an outer layer of the contact member and comprising said outer surface; whereby said contact member is adapted to behave, along said outer surface, as a material having a heat expansion coefficient essentially closer to α 1 than to α 2 .