The utility model belongs to the technical field of the bridge subtracts the shock insulation, a spacing speed lock is disclosed, being provided with the piston, the piston is arranged in the cylinderand the cylinder is passed respectively at the piston both ends, two ends of cylinder are provided with first end cover and second end cover respectively, the second end cover divides into two partswith the cylinder, and partly closed chamber who is first end cover and second end cover and cylinder and forms packs damping medium in the cavity, another part inner wall is equipped with the helicitic texture and is connected with the connecting pipe, set up the pinhole of spacer pin on the cylinder, the spacer pin passes the cylinder and is connected with the piston. The cylinder still have except setting up closed chamber one section vacant, be equipped with the pinhole on this vacant cylinder, the spacer pin passes this pinhole and piston rod and links to each other to the limit functionof realization speed lock. The cylinder except setting up closed chamber except the installation spacer pin still have one section vacant, this vacant cylinder inner wall is equipped with the helicitic texture and can be connected with the connecting pipe, can realize speed lock axial length's regulation through threaded connection.