A foldable ladder has multiple ladder segments that fold and unfold relative to each other. Each ladder segment includes one rung element and multiple side rail sections that unfold for deployment to form box-shaped side rails of the ladder. Adjacent ladder segments are connected to each other by hinge joints. The ladder includes locking features at the hinge joints for preventing relative pivoting movement of adjacent ladder segments by more than about 180 degrees.
1. A foldable ladder comprising:
a plurality of ladder segments hingedly connected to each other at a plurality of hinge joints, the ladder being configured to fold at the plurality of hinge joints between a folded stored condition and an extended straight condition, wherein the stored condition is configured to be used for storage or transportation, and the straight condition is configured to allow a user to ascend or descend the ladder during use;
the plurality of ladder segments including adjacent first and second ladder segments that are connected by a first hinge joint of the plurality of hinge joints;
each one of the first and second ladder segments including a respective rung element, the respective rung element having a rung extending laterally between and fixed to respective inner side rail sections;
the rung element of the first ladder segment being hingedly connected to the rung element of the second ladder segment by inner knuckles at the first hinge joint;
each one of the first and second ladder segments also including respective middle side rail sections and respective outer side rail sections, the respective middle side rail sections and the respective outer side rail sections being hingedly connected with the respective inner side rail sections and configured to fold relative to the respective inner side rail sections to form C-shaped side rails when the ladder is in the straight condition having a major length of each one of the C-shaped side rails extending perpendicular to a major length of each of the rungs;
the middle side rail sections on the first ladder segment being hingedly connected to the middle side rail sections on the second ladder segment by middle knuckles at the first hinge joint;
the outer side rail sections on the first ladder segment being hingedly connected to the outer side rail sections on the second ladder segment by outer knuckles at the first hinge joint;
the ladder further including locking features at the first hinge joint configured to limit unfolding of the first ladder segment with respect to the second ladder segment to about one hundred eighty degrees;
the locking features including projecting tabs on the inner knuckles of second ladder segment, and including projecting tabs on the outer knuckles of the second ladder segment, the projecting tabs configured to engage stop surfaces on the first ladder segment when the ladder is in the straight condition to limit the unfolding of the first ladder segment with respect to the second ladder segment to said about one hundred eighty degrees;
the locking features also including a plurality of locking fingers on the middle side rail sections, the plurality of locking fingers being distinguishable from the middle knuckles and having at least one set of locking fingers located laterally between at least one pair of the middle knuckles, the at least one set of locking fingers configured to: (a) engage additional stop surfaces when the ladder is in the straight condition to limit the unfolding of the first ladder segment with respect to the second ladder segment to said about one hundred eighty degrees, and (b) abut each other laterally to provide a lateral load bearing capability when in the straight condition;
the at least one set of locking fingers including first and second locking fingers on at least one of the middle side rail sections of the first ladder segment at the first hinge joint, the first and second locking fingers being spaced apart from each other laterally to define a gap; the at least one set of plurality of locking fingers also including a third locking finger located on one of the middle side rail sections of the second ladder segment at a location adjacent to the gap and between the first and second locking fingers;
the locking features including first and second stop surfaces of the additional stop surfaces on the second ladder segment at the first hinge joint, the first and second stop surfaces being located outward of and on opposite sides of the third locking finger;
the locking features also including a third stop surface of the additional stop surfaces on the first ladder segment at the first hinge joint, the third stop surface being located between the first and second locking fingers;
the first and second locking fingers on the first ladder segment being configured to project over and abuttingly engage the first and second stop surfaces on the second ladder segment, respectively, when the ladder is in the straight condition, to limit the unfolding of the first ladder segment with respect to the second ladder segment to said about one hundred eighty degrees;
the third locking finger on the second ladder segment being configured to project over and abuttingly engage the third stop surface on the first ladder segment when the ladder is in the straight condition to limit the unfolding of the first ladder segment with respect to the second ladder segment to said about one hundred eighty degrees; and
wherein, when the ladder is in the straight condition, the first, second and third locking fingers interlock and abut each other laterally to form a block configured to resist lateral loading on the ladder.