Automatic brake device of hydraulic stretcher, hydraulic stretcher and brake method

The invention discloses an automatic brake device of a hydraulic stretcher, the hydraulic stretcher and a brake method, and relates to the technical field of hydraulic stretching equipment. The automatic brake device comprises a hydraulic buffer mechanism, the hydraulic buffer mechanism comprises a first cartridge valve and a pressure regulating mechanism, and the pressure regulating mechanism comprises a control unit, a high-pressure overflow valve and a low-pressure overflow valve which are installed in parallel. The output ends of the high-pressure overflow valve and the low-pressure overflow valve are connected with the first cartridge valve, the output pressure of the low-pressure overflow valve is smaller than the pressure of the oil outlet, and the output pressure of the high-pressure overflow valve is larger than the pressure of the oil outlet. When stretching reaches a specified stroke, the control unit switches the high-pressure overflow valve to work and blocks the first cartridge valve, oil does n