Ladder section length adjusting and clamping mechanism for ladder type bridge welding machine

The utility model discloses a ladder section length adjusting and clamping mechanism for a ladder type bridge frame welding machine, which comprises a fixed seat assembly and a movable seat assembly which are oppositely arranged on a rack and are used for vertically placing two ladder sides respectively, the rack is provided with a pre-adjusting sliding driving device which drives the movable seat assembly to horizontally slide relative to the fixed seat assembly and is used for adapting to different ladder section lengths, and the pre-adjusting sliding driving device is further provided with a clamping sliding driving device which can drive the movable seat assembly to horizontally slide and is used for finally clamping and positioning the ladder sections. When the clamping and positioning device is used, large-amplitude adjustment is carried out through the pre-adjustment sliding driving device, then final clamping and positioning are carried out through the clamping sliding driving device, and through the