Patent ID: 8869939
Filing Date: 2014-10-28
Classification: E06C

Abstract:
1. An improvement of an extension ladder structure, comprising, a plurality of side rail sections which are hollow and tubular-shaped, and which telescope with each other due to different internal diameters, wherein an orientation hole is provided on an end of the side rail sections; a plurality of connection kits comprising a ring-shaped covering part which fits on an upper end of each of said side rail sections respectively, a via hole that is aligned with the orientation hole of said side rail sections is provided on the ring-shaped covering part; wherein one side of said ring-shaped covering part extends outward as a pivotal joint such that a channel is formed within the pivotal joint; a plurality of transverse step portions cover and enclose an exterior of said pivotal joint; a plurality of locking mechanisms, which are disposed within the channel of said pivotal joint, comprising: a locking bar with a first end for passing through the via hole of said ring-shaped covering part and said orientation hole of the side rail sections; a spring disposed at a second end of said locking bar so that the locking bar can return to an original location; a plate for fixing the locking bar and the spring in a location in said channel; and a turning rod for pushing said locking bar to another location; wherein a protruding ejection bar is disposed at an upper end of the ring-shaped covering part of said connection kit; said protruding ejection bar is oriented toward an opening of an upper connection kit; wherein, when the upper connection kit sticks on a lower connection kit, the protruding ejection bar of the lower connection kit pushes the turning rod within the upper connection kit so that the turning rod sways and drives the locking bar to withdraw from the orientation hole of an upper side rail section such that upper side rail sections can be telescoped in descending order, an in-protruding encircling ring part is provided at an upper tube opening of the side rail sections; an out-protruding ring part is provided at a lower tube opening of the side rail sections; and further comprising an unlocking block fitted on the protruding ejection bar, wherein a groove is provided at a lower end of the unlocking block, which is fit onto an upper end of the ejection bar; an upward protruding ejection bar extension is provided at an upper end of the unlocking block; wherein, when the unlocking block is fit onto the upper end of the ejection bar, a space will be formed after an upper transverse step portion and a lower transverse step portion are telescoped.