US Patent 7874242 Piston assembly in fluid pressure cylinder

The piston 4 comprises a fixing ring 8 mounted on a piston rod 6, and a piston body 10 fixed to the fixing ring 8. The fixing ring 8 is comprised of two semi-circular plated members 8A, 8B having plural threaded holes 8a for bolt-fastening of the piston body 10. When they are abutted against each other and formed into a circular-annular shape, a hole portion 8c which is to be tightly fitted in a fixing groove 6a of the piston rod 6 is formed. The piston body 10 has a hole portion 10a which is to be fitted over the piston rod 6, and plural bolt holes 10c corresponding to the threaded holes 8a. Moreover, the piston body 10 has a concave portion 10d on a side of one surface thereof, in which the fixing ring 8 is fitted in an embedded state.