Field configurable sonic grade control

Apparatus for controlling the height of a paving machine leveling instrument relative to a datum, said apparatus comprising:

• sonic means for transmitting sonic signals and receiving reflections of said sonic signals;
• a sonic target;
• means for storing a predetermined value corresponding to the distance between said sonic means and said target;
• means responsive to said sonic means for measuring first and second time periods wherein the first time period corresponds to the round trip travel time of a sonic signal between said sonic means and said target and the second time period corresponds to the round trip travel time of a sonic signal between said sonic means and said datum;
• means responsive to said stored target distance value and said first and second time periods for providing a datum distance signal corresponding to the distance between said sonic means and said datum;
• means responsive to said datum distance signal and a reference signal for providing a signal for controlling the height of said paving machine leveling instrument;
• and
• operator actuable means for modifying said stored target distance value to calibrate said datum distance signal.

Apparatus for controlling the position of a paving machine leveling instrument relative to a datum, said apparatus comprising:

• sonic means for transmitting sonic signals and receiving reflections of said sonic signals;
• a sonic target;
• means responsive to said sonic means for measuring first and second time periods wherein the first time period corresponds to the round trip travel time of a sonic signal between said sonic means and said target and the second time period corresponds to the round trip travel time of a sonic signal between said sonic means and said datum;
• means responsive to said first and second time periods for providing a datum distance signal corresponding to the distance between the sonic means and a datum;
• comparison means responsive to said datum distance signal and a reference signal for determining the difference between said signals and for generating a control signal in response to said difference;
• positioning means responsive to said control signal being greater than a predetermined threshold value for moving said leveling instrument;
• means for adjusting said predetermined threshold value;
• and
• a display for indicating said predetermined threshold value.

A road paver comprising:

• a leveling instrument disposed at a predetermined distance from a datum;
• means coupled to the leveling instrument for changing the position of said leveling instrument relative t said datum in response to a control signal;
• means for controlling said position changing means comprising:
• a) sonic means for transmitting sonic signals and receiving reflections of said signals;
• b) a sonic target disposed at a predetermined target distance from said sonic means;
• c) means responsive to said sonic means for measuring first and second time periods wherein the first time period corresponds to the round trip travel time of a sonic signal between said sonic means and said target and the second time period corresponds to the round trip travel time of a sonic signal between said sonic means and said datum;
• d) means responsive to said first and second time periods for providing a datum distance signal corresponding to the distance between the sonic means and the datum;
• e) comparison means responsive to said datum distance signal and a reference signal for providing the control signal in response to the difference between said signals;
• f) means for adjusting said reference signal by a predetermined increment;
• g) means for displaying said predetermined increment;
• h) means for modifying said predetermined increment in response to said control means being in a first mode of operation;
• and
• i) operator actuable means for selecting said first mode of operation.