Patent ID: 8752244

Claim:
A hydraulic damper ( 5 ; 60 ) for closing a hinged member (H) comprising: a cylinder barrel ( 19 ; 68 ); a closed cylinder cavity ( 20 ; 70 ) formed within the cylinder barrel ( 19 ; 68 ); a piston ( 21 ; 72 ) placed within the closed cylinder cavity ( 20 ; 70 ) so as to divide the closed cylinder cavity ( 20 ; 70 ) into a first side ( 20 a ; 70 a ) and a second side ( 20 b ; 70 b ); and a damper shaft ( 22 ; 62 ) coupled to the piston ( 21 ; 72 ) for dampening closing movement of the hinged member, wherein, at least at 20° C., an outer perimeter surface of the piston ( 21 ; 72 ) defines a clearance between an inner perimeter surface ( 27 ) of the cylinder barrel ( 19 ) to allow hydraulic fluid contained in the cylinder cavity ( 20 ; 70 ) to flow through the clearance between the outer perimeter surface of the piston ( 21 ; 72 ) and the inner perimeter surface of the cylinder barrel ( 19 ) between the first side ( 20 a ; 70 a ) and the second side ( 20 b ; 70 b ) of the closed cylinder cavity ( 20 ; 70 ), wherein the cylinder barrel ( 19 ; 68 ) is made of a first material, having a first thermal expansion coefficient and the piston ( 21 ; 72 ) is made of a second material having a second thermal expansion coefficient, the second thermal expansion coefficient being larger than the first thermal expansion coefficient so that the clearance decreases when the temperature of the damper ( 5 ; 60 ) is raised and increases when the temperature of the damper ( 5 ; 60 ) is lowered, and wherein the difference between the first and second thermal expansion coefficients is at least 1.5×10 −5 K −1 .