Thermo-element

A thermo-element including a thermally expandable component made of a wax mixture which is expandable and contractible by a temperature change, expansion and contraction of said wax mixture causing a piston to move in and to move out, said thermo-element comprising:

• a cylindrical casing, one end portion thereof being open for enclosing said wax mixture therein;
• a cylindrical guide member which engages said one end portion of said casing;
• a piston held inside said guide member so that said piston can slide freely;
• and
• a thick sealing member arranged between said guide member and said wax mixture for enclosing said wax mixture in said casing and for moving-in and moving-out said piston, wherein
• said thick sealing member is formed of a rubber elastomer;
• said thick sealing member has a piston insertion bore formed in a central portion thereof for supporting one end portion of said piston;
• said thick sealing member has a thin portion at a lower end portion of said piston insertion bore, an annular rib arranged at an outer peripheral region for sealing said wax mixture and a thick portion between said thin portion and said rib, the thick portion having a thickness greater than the thickness of the thin portion;
• one surface of said thick portion is in contact with a contact surface of a base of said guide member and the other surface of said thick portion is in contact with said wax mixture;
• and
• as said wax mixture expands by a temperature change, said thick portion of said thick sealing member is deformed to be displaced to under portion of said piston, said thin portion is deformed convexly upward, and both said thick portion and said thin portion thus push up said piston.