Abstract: An improved hinge for a collapsible ladder includes a pivot pin which has a sufficiently simple construction to permit it to be fabricated by die-casting on a cost-competitive basis. The simple construction is made possible by an improved axial detent arrangement for a shaft which rotates and slides within the hub and to which the hinge locking pins are secured. The detent arrangement includes a detent bore extending radially biased against the shaft. A suitable detent recess in the shaft is angularly aligned with the detent bore for each locking position of the shaft. Axial alignment of the bore and a recess is achieved by fully extending the shaft out of the hub against the restoring force of a bias spring in the hub. The recess and bias member are contoured to permit disengagement of the detent by rotation of the shaft but not by axially applied forces.

Abstract: An improved hinge for a collapsible ladder includes a pivot pin which has a sufficiently simple construction to permit it to be fabricated by die-casting on a cost-competitive basis. The simple construction is made possible by an improved axial detent arrangement for a shaft which rotates and slides within the hub and to which the hinge locking pins are secured. The detent arrangement includes a detent bore extending radially biased against the shaft. A suitable detent recess in the shaft is angularly aligned with the detent bore for each locking position of the shaft. Axial alignment of the bore and a recess is achieved by fully extending the shaft out of the hub against the restoring force of a bias spring in the hub. The recess and bias member are contoured to permit disengagement of the detent by rotation of the shaft but not by axially applied forces.

Abstract: A grinding disc for use with grinding apparatus adapted to grind grain and the like. The grinding disc includes an opening centrally located therein, with the perimeter of the opening forming a plurality of teeth projecting toward the center of the disc. The teeth are separated by generally horseshoe-shaped notches. The grinding disc further includes a plurality of groups of channels on one face thereof defining grinding ridges therebetween and extending from near the periphery of the disc inwardly to the opening in the disc. Certain of the channels in each group intersect with certain other channels in at least one other group to form a cross-hatching of channels.