US Patent 11319751 Telescopic positioning structure used for ladder

A telescopic positioning structure used for a ladder is disclosed. The ladder includes a front supporting leg and a rear supporting leg. The front supporting leg includes a first tube and a second tube, and the first tube and the second tube are able to move relative to each other in an extension direction. The rear supporting leg is rotatably connected with the first tube. The ladder further includes a pin connected with the first tube. When the rear supporting leg is unfolded, an upper end of the rear supporting leg abuts against the pin and drives to the pin to move towards the second tube, and when the pin abuts against the second tube, the second tube is positioned.