Multi-position safety lock joint, particularly for folding ladders

Claim 1

Multi-position safety lock joint, particularly for use with folding ladders, having a first, at least partly circular joint element (2) formed with peripheral notches (5), a second, at least partly circular joint element (1), a pivot member (3) passing through the center of said joint elements and connecting them together; a resiliently biased locking element (6) located on the second joint element (1) and engageable with the notches (6) in the first joint element (2) to lock the two joint elements in relatively fixed position; an operating handle (10, 12) pivoted (11) on the second joint element (1) having a manually operated portion (12) extending beyond the joint for manual operation thereof and an engagement portion (10) engageable with the locking element (6) to disengage the locking element from the notch (5); and holding means (14) resiliently positioned and engageable with the handle (10, 12) in a first position to hold the handle in the position in which the locking element (6) is disengaged from a notch and, upon relative pivoting movement of the joint elements (1, 2), is released from the first engaged position with the handle to permit the locking element (6) to engage in a notch (5) and to lock the joint against relative rotation; wherein the holding means (14) comprises a disk (14) rotatable on the pivot member (3); a spring (16) is provided secured to the joint and holding said disk (14) in a position other than said first position, said disk being formed with projecting holding teeth (17) and located relative to the notches (5) on said first joint member (1) and the engagement portion (10) of the handle to be engaged by said engagement portion of the handle and rotate counter the force of said spring (16) upon movement of the handle to release the locking element (6) from a notch (5), the teeth (17) of said disk and the engagement portion (10) of said handle being shaped to release the disk (14) from engagement with the handle when the handle has moved in the locking member position so that a respective tooth will be moved in interfering position with the handle to block pivoting movement of the handle until a notch (5) of the first member is in position to receive the locking member (6) located on the second member (1).