Apparatus and method for controlling laser guided machines

An improved guidance system for increasing the control accuracy of a laser guided machine of the type having a machine element to be controlled and positioned with respect to a laser beam, a laser beam receiver mounted on the machine element for generating electrical signals in response to the laser beam impinging thereon, a fluid cylinder having a piston therein movable by fluid acting against opposite sides of the piston and mounted on said machine element and operable to move the machine element with respect to the laser beam, and electrically controlled fluid valve means for directing fluid to and from the fluid cylinder, and electrical control means connected to the receiver and the hydraulic valve for operating the fluid valve in response to movement of the machine element and receiver with respect to the laser beam, said improvement comprising:

• said electrically controlled fluid valve means directing fluid continuously to and from said fluid cylinder to move said piston, said fluid valve means having two sets of valve ports, each set having a pair of valve ports which are movable between open and closed positions and electrical drive means for moving said valve port sets between their open and closed positions;
• one of said valve port sets being connected to one side of the fluid cylinder piston;
• the second of said valve port sets being connected to the opposite side of the fluid cylinder piston;
• said one valve port set being normally open and directing fluid to and from the fluid cylinder to move the machine element and laser beam receiver in one direction from a first position to a second position;
• said second valve port set being normally closed and preventing fluid from being directed to and from the fluid cylinder;
• the electrical control means including circuit means connected to said electrical drive means for moving said valve port sets to their respective opposite closed and open positions in response to the laser beam receiver and machine element reaching said second position such that said second valve port set will be open and direct fluid to and from the fluid cylinder to move the machine element and laser beam receiver in a direction opposite to said one direction from said second position back to said one position, whereby the machine element will continuously cycle between said first and second positions while reducing the dead band of the system.

A method for increasing the accuracy of and controlling a laser guided machine, the machine having a movable machine element positioned in response and relative to a laser reference beam located externally of the machine, the method including:

• sensing the laser reference beam with a laser beam receiver on the machine element when said laser beam receiver is in a first centered region with respect to the laser reference beam and in a second off-center region;
• providing a first electrical condition with an electrical circuit means connected to the laser beam receiver on the machine when the machine element and laser beam receiver are in said first centered region and a second electrical condition with the electrical circuit means when the machine element and laser beam receiver are in said second off-center region;
• controlling a motive power means to continuously move the machine element and laser beam receiver between said first and second regions, said controlling including operating the motive power means to move the machine element and laser beam receiver in a first of two directions from said first region to said second region in response to said electrical circuit means being in said first condition, and operating the motive power means to move the machine element and laser beam receiver in the second of said two directions from said second region back to said first region in response to said electrical circuit means being in said second condition;
• whereby the machine element is cycled continuously between said first and second regions while reducing the dead band of the system.

A method for increasing the accuracy of and controlling a laser guided machine having a movable machine element and a hydraulic/electrical control system, said method comprising:

• sensing a laser reference beam with a laser beam receiver located on and movable with the machine element when the receiver is in a first centered region with respect to the laser reference beam and in a second off-center region with respect to the laser reference beam;
• providing a first electrical condition with an electrical circuit means connected to the laser beam receiver on the machine when the machine element and laser beam receiver are in said first centered region and a second electrical condition with the electrical circuit means when the machine element and laser beam receiver are in said second off-center region;
• setting an electrically operated fluid valve connected to said electrical circuit means to direct fluid continuously to and from a fluid cylinder to move the machine element and laser beam receiver between said first and second regions, said setting including positioning the fluid valve in a first position to direct fluid to the fluid cylinder to move the machine element and laser beam receiver in a first of two directions from said first centered region to said second off-center region in response to said first electrical condition, and positioning the fluid valve in a second position to direct fluid to the fluid cylinder to move the machine element and laser beam receiver in the second direction from said second to said first region in response to said second electrical condition;
• whereby the machine element is cycled continuously between said first and second regions while reducing the dead band of the system.

A guidance system for a laser guided screeding apparatus, said apparatus including a screed for spreading and/or smoothing loose or plastic material such as uncured concrete, and elevation means for raising and lowering said screed relative to a laser reference beam located externally of said apparatus, said system comprising:

• laser beam receiving means mounted on and movable with said screed for sensing the laser reference beam in a first, centered, on target region and in a second, off-center region of said receiving means;
• electrical circuit means connected electrically to said laser beam receiving means for providing a first electrical condition when said screed and said laser beam receiving means are in said first on target region and a second electrical condition when said screed and said laser beam receiving means are in said second region;
• said elevation means adapted to raise and lower said screed and laser beam receiving means between said first on target region and said second off-center region;
• and
• control means connected electrically to said electrical circuit means and mounted on said screed for continuously operating said elevation means to move said screed and laser beam receiving means between said first and second regions, said control means operating in response to said electrical circuit means to move said screed and laser beam receiving means from said first on target region to said second off-center region when said electrical circuit means provides said first condition, and for operating said elevation means to move said screed and said laser beam receiving means from said second off-center region back to said first on target region when said electrical circuit means provides said second condition, whereby the machine element will continuously cycle between said on target and off-center regions while reducing the dead band of said system.

A method for increasing the accuracy of and controlling a laser guided screeding apparatus, the screeding apparatus having a movable screed positioned in response and relative to a laser reference beam located externally of the machine, the method including:

• sensing the laser reference beam with a laser beam receiver on the screed when said laser beam receiver is in a first, on target, centered region with respect to the laser reference beam and in a second or low, off-center region;
• providing a first electrical condition with an electrical circuit means connected to the laser beam receiver on the screeding apparatus when the screed and laser beam receiver are in said first on target, centered region and a second electrical condition with the electrical circuit means when the screed and laser beam receiver are in said second, off-center region;
• controlling an elevation means to continuously move the screed and laser beam receiver between said first on target region and said second off-center region, said controlling including operating the elevation means to move the screed and laser beam receiver from said first on target region to said second off-center region in response to said electrical circuit means being in said first condition;
• and operating the elevation means to move the screed and laser beam receiver from said second off-center region back to said first on target in response to the electrical circuit means being in said second condition;
• whereby the screed is cycled continuously between said on target and off-center regions while reducing the dead band of the system.