AN EXTENSION LADDER AND ITS USE IN A STRAIGHT COMBINATION LADDER, A PLATFORM LADDER OR A STEPLADDER

摘要

An extension ladder (100), including multiple ladder sections vertically fit to each other, each ladder section including a pair of columns (101) dispose on both sides thereof and a rung (102) connected thereto, diameters of the columns (101) on both sides increasing from the top to the bottom, a pair of pin holes being disposed on the column (101) and engaged to a latch gear (104) in the rung (102). The latch gear (104) includes a pair of drive wheels (109, 111), a pair of transmission parts (110,112), and a pair of pins (105) disposed on both ends thereof. A self-locking part (106) is disposed on the pin (105). Rotation of the drive wheels (109, 111) drives the pins (105) to move axially via the transmission parts (110, 112). Multiple extension ladders can form a vertical ladder, a step ladder, or a platform ladder.