US Patent 7255038 Piston for automatic transmission

A piston for an automatic transmission includes: (a) a cylindrical wall portion provided by a first piston member; (b) a bottom wall portion provided by a second piston member; and (c) an engaging portion at which the first and second piston members are engaged with each other such that the first piston member is movable relative to the second piston member in an axial direction of the piston by a small distance. The piston is characterized by further including (d) an elastic structure which is provided at the engaging portion, and which biases the first piston member in the axial direction, so as to restrain movement of the first piston member relative to the second piston member in the axial direction.