Hydraulic cylinder with press-fitted pipe

In a hydraulic cylinder wherein a bottom is provided at one end of a cylinder, a cap is provided at the opposite end of the cylinder, a hollow piston is inserted movably into the cylinder, a piston rod is also inserted movably into the cylinder through said cap, said piston defines a rod-side oil chamber and a piston-side oil chamber within the cylinder, said rod-side oil chamber communicating with a reservoir in said piston rod through an oil hole formed in the lower portion of the piston rod, a pipe extending into said reservoir is mounted upright on the upper end portion of the piston, a relief valve for opening and closing said reservoir and said piston-side oil chamber is disposed in the hollow portion of the piston, and said piston- side oil chamber communicates selectively with a pump or a tank, the improvement characterized in that a spigot portion is mounted upright integrally in the center of the upper end portion of the piston, the base end of the piston rod is fitted on the outer periphery of said spigot portion, the outer periphery of the base end of said pipe is press-fitted into an upper part of the hollow portion of said spigot portion, a hollow oil bore rod is mounted upright integrally in the center of the upper end of said bottom, and a cushion ring is provided on the inner periphery of the lower hollow portion of the piston so as to be fitted on the outer periphery of said oil bore rod, said cushion ring defines an axial cut-out formed on an outer periphery of the cushion ring, said cushion ring is mounted axially movable in said hollow portion of said piston, said cushion ring has a cushion effect and a check valve function.

A hydraulic cylinder comprising:

• a cylinder having ends;
• a bottom arranged at one said end of said cylinder;
• a cap arranged at another said end of said cylinder;
• a piston arranged movably in said cylinder, said piston dividing an area in said cylinder into a rod side chamber and a piston side chamber, said piston defining a hollow portion;
• a piston rod arranged movably in said cylinder and through said cap, said piston rod defines a reservoir and an oil hole, said rod-side chamber communicating with said reservoir in said piston rod through said oil hole;
• a spigot mounted integrally in, and extending from, a center of a rod side of the piston, said spigot defining a hollow portion, said hollow portions of said piston and said spigot communicating said reservoir and said piston side chamber, said piston rod being press-fitted onto an outer periphery of said spigot;
• a relief valve in said piston and for opening and closing communication through said hollow portions of said piston and said spigot;
• a pipe press fitted into said hollow portion of said spigot and extending from said piston into said reservoir.