The prior art reveals a considerable number of devices designed to spread materials over the ground or over existing layers of material where it is desirable to obtain a finished grade. All of the known apparatus of this kind are towable behind a tractor or similar vehicle. Such a device is disclosed in U.S. Pat. No. 6,308,785 to Rhoden, issued Oct. 30, 2001.
Machines similar to the Rhoden grader/spreader are satisfactory for their intended agricultural purposes but have limitations when applying and spreading materials for road and highway construction. The depth or thickness of layers of gravel and other materials that comprise a road or highway are carefully specified by the design engineers. In many cases the depth requirement is a minimum figure and unintended deposition of a greater amount of material is wasteful and overly expensive. For example, many excess cubic yards of material would be consumed if one inch of material in excess of the specification is applied to a multi-mile roadway thirty feet wide.
When a grader/spreader is pulled by a vehicle it can be assumed that the towing vehicle is going to traverse surface variations that are going to cause the grader/spreader to undulate in response to the pitching motions of the towing vehicle. Where the work is being done to construct or resurface a road or highway the rising and falling movement of the grader results in an uneven surface on the material being spread, together with significant departures from the design specification. Agricultural endeavors do not require the grader precision that must be present in road and highway work.
Accordingly, it is an object of the present invention to provide a grader/spreader that is pushed by a vehicle that runs on the graded surface provided by the grader/spreader it is pushing.
Another object of the invention is to provide a grader whose blade elevation and grading angle is adjustable by the operator of the vehicle that is pushing the grader.
Other objects, features and advantages of the grader of the present invention will become apparent upon a reading the following specification taken in conjunction with the attached drawings.