Patent ID: 6286641
Filing Date: 2001-09-11
Classification: F16F

Abstract:
An oil brake comprising a piston, a movable tubular rod, a brake stem, a hollow cylindrical body, said piston being mounted to and adjacent a free end of said movable tubular rod for movement in said cylindrical body, an opposite end of said tubular rod being connected with said brake stem whereby said tubular rod moves in said hollow cylindrical body and defines on opposite sides of said piston a first working volume and a second working volume, a central rod disposed inside said tubular rod, said tubular rod having at least one lateral opening connecting said second working volume and said first working volume to one another via at least one central passage between said tubular rod and said central rod formed by a relative difference in transverse dimensions between said central rod and an inside diameter of said tubular rod, said one opening being formed on said tubular rod a distance from said piston equal to at least one-half of the thickness of said piston, a stem guide closing an end of said cylindrical body and configured such that, during an expansion stroke and before the end of said expansion stroke displacing said piston along said cylindrical body toward said stem guide, said one opening formed on said tubular rod is sealed by an internal wall of said stem guide before all of the oil is evacuated from said second working volume toward said first working volume forming an oil pocket sufficiently thick to constitute a hydraulic cushion for said piston, said tubular rod having four openings connecting said second working volume and said first working volume to one another, said four openings being located a distance from the piston substantially equal to the thickness of the piston whereby said central passage is formed by a reduction in the diameter of said central rod at an end thereof that opens into said first working volume.