Self-locking bi-foldable load bearing segment
Self-locking bi-foldable load bearing segments are disclosed that can be used in applications such as ladders or ramp. First and second sections of the segment are foldably coupled to transition between an open configuration and a folded configuration. The first and second sections can include rungs pivotally attached to rails that can be further transitioned from the folded configuration to a collapsed configuration, but not transitioned from the open configuration to the collapsed configuration. Openings in the side walls of the rails allow the rungs to pivot in one direction, but not an opposite direction. In the open configuration, the openings of the first and second sections may be oriented opposite, and the direction of allowed rotation of the rungs of the first section and second section are opposite, restricting compression of the rails together. In the folded configuration, the openings of the first and second sections can be oriented the same to allow rotation of the rungs and compression of the rails together.
1. A self-locking, bi-folding load bearing segment, the load bearing segment comprising:
a first section comprising a first rail, a second rail, and a first plurality of hollow tubular rungs pivotally attached to and extending between the first and second rails in a parallelogram linkage, such that a separation between the first and second rails is adjustable between an un-collapsed configuration with the rungs generally perpendicular to the first and second rails and a collapsed configuration with the rungs at an angle of less than 30 degrees relative to the first and second rails, the first and second rails restricting rotation of the first plurality of rungs from the un-collapsed to the collapsed configuration to a first direction relative to a front face of the load bearing segment;
a second section comprising a third rail, a fourth rail, and a second plurality of rungs pivotally attached to and extending between the third and fourth rails in a parallelogram linkage, such that a separation between the third and fourth rails is adjustable between the un-collapsed configuration with the rungs generally perpendicular to the third and fourth rails and the un-collapsed configuration with the rungs at an angle of less than 30 degrees relative to the third and fourth rails, the third and fourth rails restricting rotation of the second plurality of rungs from the un-collapsed to the collapsed configuration to a second direction opposite the first direction relative to the front face of the load bearing segment;
a first hinge pivotally attaching the first ladder rail to the third ladder rail; and
a second hinge pivotally attaching the second ladder rail to the fourth ladder rail, wherein the first and second hinges allow the first and second sections to be rotated between an open configuration to the folded configuration,
wherein the first and second plurality of rungs on the first and second segments rotate in the same direction relative to the rails when in the folded configuration to permit the rails to be moved between the un-collapsed configuration to the collapsed configuration, and
wherein the first and second plurality of rungs on the first and second segments rotate in opposite directions when in the open configuration to automatically lock the first and second segments in the un-collapsed configuration, wherein no separate locking mechanism is required to lock the first and second plurality of rungs in the un-collapsed configuration when the load bearing segment is in the open configuration.
2. The load bearing segment of claim 1 wherein each of the first rail, the second rail, the third rail, and the fourth rail comprise an inner wall configured to engage the rungs and an outer wall configured to shield a user from contact with ends of the rungs.
3. The load bearing segment of claim 1 comprising openings in the inner walls of the rails that restrict rotation of a plurality of the rungs between the un-collapsed configuration and the collapsed configuration.
4. The load bearing segment of claim 3 each rung engages with at least one opening in the inner walls of the rails.
5. The load bearing segment of claim 1 wherein the rails comprise an inner wall and an outer wall that shields a user from where the rungs engage the inner walls.
6. The load bearing segment of claim 1 wherein the open configuration of the load bearing segment is load bearing in a direction against the front face of the rails and the rungs.
7. The load bearing segment of claim 1 wherein the load bearing segment is load bearing in a direction parallel to a longitudinal axis of the rails in the open configuration.
8. The load bearing segment of claim 1 wherein the load bearing segment is one of a ladder or a ramp.
9. The load bearing segment of claim 1 wherein the rails comprise a “C-shape” cross section with a channel oriented to receive ends of the rungs.
10. The load bearing segment of claim 1 wherein each of the rails comprise one or more tabs protruding out from the front surface of the rail to define a recess on the front surface in which a securement device for securing the rungs to the rail is recessed.