This invention relates generally to techniques for moving a heavy load by moving a supporting floor beneath the load and, more particularly, to techniques for moving a heavy load supported on a floor consisting of multiple movable stairs. If, for example, all of the slats are moved together in one direction, the load will be carried in that direction, but if the slats are returned to their starting positions in smaller groups containing only a fraction of the total number of slats, then the frictional forces between the load and a returning group of slats will be insufficient to move the load in the reverse direction.
Moving floors of this type have a number of useful applications, one of which is in the collection and disposal of garbage or waste. In large cities, long distances to disposal sites have resulted in the increased use of large transfer trailers, for the temporary storage of waste gathered by collection vehicles. When a transfer trailer is full, it is towed to a disposal site for emptying. Emptying such a vehicle by tipping is cumbersome and difficult if a large trailer is used, movable floors provide an ideal solution. Typically, a rear door of the trailer is opened and the waste material is ejected through the door by operation of the moving floor.
Systems in use prior to the present invention are sometimes referred to as "walking" floors and operate by moving all of the slats in the desired direction as far as they can travel, and then returning each slat one at a time. These systems incorporate relatively simple hydraulic control techniques and, when a hydraulic cylinder reaches the limit of its travel, the fluid flow from a hydraulic pump must be bypassed to a holding tank until valves can switch the cylinder in the appropriate direction. The time required for unloading with these systems is typically 15-20 minutes, which is considerably longer than desired.
The principal disadvantage of prior systems of this general type is that the load movement is started and stopped repeatedly, which is clearly inefficient and time consuming. The time to unload is at least twice as long as it would be if the load could move continuously. In addition there are hydraulic control system disadvantages, in that the oil tends to overheat due to the need for bypassing the pump at the end of all of the strokes before the hydraulic cylinders can switch. Moreover, rather large pump flow rates are required to gain reasonable speeds. The present invention overcomes all of these disadvantages.
It will be appreciated there is a need for improvement in the field of movable floors. In particular, there is a need for a movable or walking floor that operates in a more continuous and efficient manner. The present invention fulfills this need and has other advantages that will become apparent from the following summary.