Safety joint mechanism, particularly for folding ladders

Claim 1

A safety joint mechanism for folding ladders, comprising: a first joint member including a disk-shaped portion comprising a pair of spaced apart, symmetrically disposed circular plates, a tubular portion extending from said disk-shaped portion and including a pair of opposing, spaced apart sides in each of which is formed a rectangular slot, a pawl slidably supported in said slots, spring means for biasing said pawl in a first direction, a pivotable operating lever including a manually actuable handle portion and a pawl-actuating fork-shaped portion engageable with said pawl when said handle portion is actuated, for pushing said pawl opposite said first direction against the bias of said spring, and a resilient leaf spring mounted on a rivet in said pair of sides of said tubular portion at a location between said slots and said handle portion and including a bent portion in the form of a lug being pressed closely against the side face of said pawl when the latter is in engagement with a notch and snap-engaging the terminal face of said pawl when the latter is being disengaged from such notch by said pawl-actuating portion, a second joint member mounted to said first joint member for relative rotation about an axis of rotation, said second joint member comprising a hollow flat locking disk element including a plurality of circumferentially spaced notches on its outer periphery, said disk element disposed between said circular plates and being connected thereto by a pivot pin defining said axis of rotation, said pivot pin extending centrally through said disk element and said circular plates such that relative rotation between said disk element and said circular plates sequentially orients said pawl in alignment with said notches, and a tubular portion extending from said disk element.