Fluid cylinder with cooling passages

A fluid cylinder comprising

• a cylinder case having a front wall at a front end and a rear wall at a rear end and a cylinder chamber formed within said case;
• a piston slideably received in said cylinder chamber;
• a piston rod connected to said piston and passing through a through-hole in said front wall of said cylinder case;
• a front sealing member mounted on an internal surface of said through-hole for sealing a clearance between said front wall and said piston rod;
• means defining a fitting hole in said piston and piston rod;
• a fitting rod mounted in said rear wall and extending forwardly from an inside face of said rear wall, said fitting rod being slidably received in said fitting hole in said piston and piston rod;
• said fitting hole including a space positioned radially inside said sealing member between a front end face of said fitting rod and an inner end of said fitting hole;
• and
• said fitting rod including means defining a feed passage for feeding fluid into said space and a separate discharge passage for discharging fluid from said space while fluid is being fed into said space.