Hinge on ladder

Abstract

A hinge on a ladder comprises outer casing pair, inner casing pair, a fixing plate with a shaft and three lock pins, a central rivet pin, and a button knob. The outer casing pair and the inner casing pair are pivotally engaged to each other in such a way that the circular plate portions on the casing pairs facially contact with one another. When the locating holes on the outer casing pair align with three specific ones of nine locating holes on the inner casing pair, the three lock pins are pushed toward the outer casing pair and to pass through the aligned locating holes and perform a locking position. When the button knob is pressed toward the outer casing pair against the restoring force of the spring, the three lock pins move away the locating holes. Therefore, the elongated projection ends of the three lock pins fit with the elongated slots on a half piece of outer casing pair to perform an unlocked position.

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