Abstract: Disclosed are a method and a device for detecting a position of a piston rod, a hydraulic cylinder and a working machine. The method includes: acquiring a target image at a target position; obtaining a pixel information corresponding to the target image; comparing the pixel information with a pixel database of the piston rod, a full-stroke pixel information of the piston rod and a relationship between the full-stroke pixel information of the piston rod and a displacement of the piston rod are stored in the pixel database of the piston rod, and the full-stroke pixel information at least comprises the pixel information within a range in which the piston rod is configured to move relative to the target position; and determining a position information of the piston rod based on a comparison result.

Abstract: A water resistance apparatus used for an oil cylinder, the oil cylinder including a press cover (10) and a piston rod (20) passing within press cover (10), and the water resistance apparatus including: a fluid inlet (14), which is arranged on the press cover (10); a fluid outlet (16), which is arranged on the press cover (10), the fluid outlet (16) and the fluid inlet (14) being in a staggered arrangement; a seal assembly (30), the seal assembly (30) being arranged between the press cover (10) and the piston rod (20); a fluid input assembly (40), the fluid input assembly (40) being connected with the fluid inlet (14); a fluid output assembly (70), the fluid output assembly (70) being connected with the fluid outlet (16).