Paving machine having automatic metering screed control

A paving machine comprising:

• a frame;
• means for propelling said frame over a surface to be paved;
• distributing means, carried by said frame, for providing a volume of unhardened concrete on the surface beneath said frame;
• a metering screed carried by said frame and adapted to engage and meter out concrete at a selected target depth over the surface beneath said frame;
• a plurality of sensors carried by said frame and adapted to produce measurements of the distance between said sensors and the surface of the concrete at an area behind said metering screed;
• link means, connected to said metering screed and said sensors, for vertical movement of said sensors in response to vertical movement of said metering screed, the vertical movement of said sensors being substantially opposite to the vertical movement of said metering screed;
• and
• control means, operatively connected to said sensors and said metering screed, for positioning said metering screed to change the volume of concrete being metered out by said metering screed, said control means being adapted to receive the sensor measurements and a tolerance from an operator of the paving machine, the tolerance being a range of distances corresponding to a selected depth for the concrete;
• wherein said control means re-positions said metering screed in response to out-of-tolerance sensor measurements.

A method of metering out unhardened concrete onto a surface to be paved, the method comprising the steps of:

• providing a paving machine having a vertically movable metering screed and means for distributing a volume of unhardened concrete beneath the paving machine in front of the metering screed;
• providing a vertically movable sensor for measuring the actual distance from the sensor to the upper surface of the concrete immediately behind the metering screed;
• determining a minimum distance and a maximum distance corresponding to an acceptable range of depth for the concrete;
• lowering the metering screed when the actual distance is less than the minimum distance and raising the metering screed when the actual distance is greater than the maximum distance;
• and
• moving the sensor in correspondence with movement of the metering screed such that the vertical movement of the sensor is substantially opposite to the vertical movement of the metering screed.