Apparatus and method for subgrade preparation

A method for leveling, grading and/or compacting a subgrade surface for receiving a preformed concrete slab on the subgrade to repair a concrete surface above the subgrade surface, said method comprising:

• providing a subgrade preparation apparatus comprising a base unit positionable on the concrete surface being repaired and a screed head assembly having a plow which defines at least one end, said screed head assembly having no major projections extending laterally outwardly from said at least one end of said plow;
• vertically moving said screed head assembly relative to said extendable boom into a cut out area of the concrete surface defining the subgrade;
• generally horizontally moving said screed head assembly along the subgrade;
• and
• grading, leveling and/or compacting the subgrade surface close to the walls of the cut out area with at least one of said plow, a means for moving material to one side of said screed head assembly and a vibrator of said screed head assembly.

A subgrade preparation apparatus for leveling, grading and/or compacting a subgrade surface for receiving a preformed concrete slab on the subgrade to repair a concrete surface above the subgrade surface, said subgrade preparation apparatus comprising:

• a base unit positionable on a concrete surface being repaired;
• an extendable boom extending from said base unit;
• and
• a screed head assembly adjustably mounted on said extendable boom, said screed head assembly being vertically adjustable relative to said extendable boom to be lowered into a cut out area of the concrete surface, the cut out area defining a subgrade surface below the concrete surface, said screed head assembly including a framework and at least one of a plow, a means for moving material toward at least one side of said screed head assembly and a vibrator mounted to said framework for grading, leveling and compacting the subgrade surface;
• a pair of spaced apart actuators mounted on said extendable boom and connected to said screed head assembly at spaced positions on said screed head assembly, said actuators being operable to extend and retract to vertically move said screed head assembly relative to said extendable boom and said base unit;
• and
• a tilt limiting device which is operable to detect a degree of tilt of said screed head assembly and to deactuate at least one of said pair of actuators in response to a threshold degree of tilt of said screed head assembly.

A subgrade preparation apparatus for leveling, grading and compacting a subgrade surface for receiving a preformed concrete slab on the subgrade to repair a concrete surface above the subgrade surface, said subgrade preparation apparatus comprising:

• a base unit positionable on the concrete surface being repaired;
• an extendable boom extending from said base unit;
• and
• a screed head assembly adjustably mounted on said extendable boom, said screed head assembly being vertically adjustable relative to said extendable boom, said screed head assembly including a framework, an auger device for moving material toward at least one side of said screed head assembly and at least one of a plow and a vibrator mounted to said framework for grading, leveling and/or compacting the subgrade surface, said auger device including a rotatable portion rotatably mounted to and extending laterally across said framework and a drive motor for rotatably driving said rotatable portion, said rotatable portion having at least one outer end, said drive motor being positioned at least partially laterally inboard of said at least one outer end of said rotatable portion such that said screed head assembly is operable to grade, level, compact and/or smooth the subgrade surface close to at least one wall at least partially surrounding the subgrade surface.