Floor structures for storage distribution areas

Claim 1

IN COMBINATION, A CART HAVING AT LEAST ONE CART-WHEEL ON WHICH THE CART CAN BE ROLLED, A CONFINEMENT AREA HAVING A SUBSTANTIALLY FLAT STATIONARY FLOOR, A BOUNDARY BARRIER FOR CONFINING SAID CART TO SAID AREA, SAID BOUNDARY BARRIER BEING INTERRUPTED TO PROVIDE A PASSAGE PERMITTING DEPARTURE OF PERSONS FROM SAID AREA, AND A THRESHOLD MEMBER FOR SAID PASSAGE ACTING TO IMPEDE MOVEMENT OF SAID CART THROUGH SAID PASSAGE, SAID THRESHOLD MEMBER HAVING A STATIONARY BASE ELEMENT AND A PLURALITY OF PROJECTIONS PROJECTING UPWARDLY FROM SAID BASE ELEMENT WITH THEIR TOP SURFACES SUBSTANTIALLY IN THE PLANE OF THE FLOOR, SAID PROJECTIONS BEING SPACED TO EXPOSE A PLURALITY OF UNIFORMLY SPACED PARALLEL STRIPS OF EQUAL WIDTH OF SAID BASE ELEMENT, SAID CART-WHEEL HAVING A RIM WIDTH LESS THAN THE WIDTH OF STRIPS, WHEREBY WHEN SAID WHEEL-RIM ROLLS FROM SAID AREA ON TO ONE OF SAID STRIPS THE WHEEL-RIM DROPS BETWEEN PAIRS OF SAID PROJECTIONS, SAID CART HAVING A BRAKE-SHOE POSITIONED WHEN SAID CART IS ON SAID FLOOR TO CLEAR THE FLOOR BY A DISTANCE LESS THAN THE HEIGHT OF SAID PROJECTIONS, SAID BRAKE-SHOE BEING POSITIONED WHEN SAID WHEEL-RIM IS BETWEEN SAID PROJECTIONS TO ENGAGE THE UPPER SURFACE OF AT LEAST AN ADJACENT ONE OF SAID PROJECTIONS TO RESTRAIN MOVEMENT OF SAID CART THROUGH THE PASSAGE, SAID PROJECTIONS BEING FORMED BY PLURAL SETS OF GROOVES, EACH OF SAID SETS COMPRISING A PLURALITY SETS OF GROOVES, SPACED, STRAIGHT, PARALLEL GROOVES EXTENDING IN A HORIZONTAL DIRECTION, THE HORIZONTAL DIRECTIONS OF SAID SETS BEING ANGULARLY SPACED FROM EACH OTHER.