Three-linkage lifting ladder

Abstract

The invention discloses a three-linkage lifting ladder, which comprises an upper ladder and a lower ladder, wherein the upper ladder consists of two upper ladder bars and a plurality of ladder rungs; the lower ladder consists of two lower ladder bars and a plurality of ladder rungs; a middle ladder is arranged between the upper ladder and the lower ladder; the middle ladder consists of two middleladder bars and a plurality of ladder rungs; the lower ladder is as wide as the upper ladder, and the middle ladder is narrower than the lower ladder and the upper ladder; a first lifting pulley device for pulling up the upper ladder is arranged between the upper ladder and the middle ladder, and a second lifting pulley device for pulling up the middle ladder is arranged between the middle ladderand the lower ladder; and a pair of returning devices capable of locking the ladder to the required height during pulling up and releasing the locking position during dropping to drop the ladder are arranged on the upper ladder bars and the middle upper ladder bars. The ladder is slightly longer than a single section after being contracted, can rise and drop, has adjustable height and is convenient for automobile transportation and collection.

Description

technical field [0001] The invention relates to a ladder, in particular to a three-connected elevator. Background technique [0002] Most of the commonly used ladders above 6 meters use two-connected telescopic lifts. Its advantages are that it can be lifted and lowered, the height can be adjusted, and the length is small after contraction for easy handling. Its structure usually has two kinds: [0003] The first type: the profile of the inner ladder side is U-shaped, the outer side column is mountain-shaped, and the inner side is slid in a groove of the outer side. It is characterized in that the structure is simple, the sliding of the inner and outer layers does not need additional slideways, and it is easy to manufacture. The disadvantage is that the outer ladder side is made of more materials and has a large bending cross-sectional area. Its strength is much higher than that of the inner ladder side, resulting in different strengths between the upper and lower sections...

AI Technical Summary

Problems solved by technology

The disadvantage is that the outer ladder side is made of more materials and has a large bending cross-sectional area. Its strength is much higher than that of the inner ladder side, resulting in different strengths between the upper and lower sections. help load-bearing standard

This construction wastes material uneconomically and the ladder is not strong enough

The second type: both the inner and outer ladder sides are rectangular. This kind of ladder side structure saves the most materials. The disadvantage is that the ladder sides themselves cannot be engaged with each other to form a slideway, and an additional slideway is required.

[0004] Their common defect of above-mentioned two stretching ladders is: the one, because they contract half at most, to especially superhigh ladder, still be inconvenient to carry, especially can't transport with small car in the city; Reasonable, unable to take into account the relationship between the strength of the ladder and the sliding structure of the ladder side

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