35 sandwiched between them as shown in fig4 the spring seal 35 is an annular ring of thin sheet metal and includes a fixed portion 35a having a plurality of holes through which the rivets 20 are fitted an outer cylindrical portion 35b extending from the fixed portion 35a toward the transmission and a resilient portion 35c spreading outward from an outer cylindrical portion 35b the resilient portion 35c is in contact with an inner circumferential end of the second power input plate 14 on a side close to the engine to urge it toward the transmission the spring seal 35 seals the fluid space a between the second power input plate 14 and the flywheel 3 the center hole in the inner circumferential end of the first power input plate 13 is fitted on the boss 15 and fixed by for instance welding as shown in fig1 an outer circumferential surface 15a of the boss 15 close to the engine is fitted in the center hole 2a of the flexible plate 2 the boss 15 is provided with a center hole 15c extending through in an axial direction and a hole 15b extending in a radial direction to lead to the center hole 15c and the fluid space a a rivet 16 is fitted through the center hole 15c in assembling the device the center hole 15c and the hole 15b are utilized to fill the fluid space a with the viscous fluid the bearing 17 is placed between an outer circumferential surface of the boss 15 close to the transmission and an inner circumference of the fly wheel.