Control system for road grader

Abstract

A control system for a road grader adapted to maintain the working edge of the grader blade in a preset datum plane so as to establish a uniform graded condition of the surface worked by the blade, regardless of the inclination assumed by the motor grader or the relative angular position of the blade itself. The system includes grade sensor means mounted adjacent one end of the blade to follow a pre-selected grade datum, slope sensing means mounted in fixed relation with the blade for keeping the blade at a predetermined slope with rotation sensing means mounted on the blade supporting ring or circle to detect the relative angular position of the blade. The rotation sensing means provides a correction signal for maintaining the slope angle of the blade at a value which will keep the "cross slope" of the surface established at a predetermined value regardless of the rotary position of the blade relative to the direction of travel.

The embodiments of the invention in which a particular property or privilege is claimed are defined as follows: 
     
       1. In a traveling machine having a movable frame, an elongated surface working element supported by said frame, and adjustment means on the machine to independently adjust the elevation of each end of the element and its rotational position relative to said frame, said machine being adapted to establish a planar surface having a predetermined cross .[.shape.].  .Iadd.slope .Iaddend.angle defined as the angle between the surface established and a horizontal plane, said angle being located in a vertical plane perpendicular to the direction of travel of the machine, a control system comprising in combination; grade sensing and control means operatively associated with said working element and said adjustment means for sensing a present grade datum and maintaining one end of said working element at a predetermined elevation related to said grade datum during travel of the machine,   a slope sensing unit operatively associated with said working element and having means to produce a slope signal proportional to the degree of inclination of said element relative to a horizontal plane,   input slope signal means providing a constant signal of predetermined value corresponding to the desired slope angle of the working element,   slope signal mixing means adapted to produce a difference signal representing the difference between said input slope signal and said sensed slope signal,   slope control means responsive to said difference signal for controlling said adjustment means for correcting the elevation of the other end of said working element to maintain said desired slope angle, and   position sensing means operatively associated with said working element and responsive to the rotary position of said working element relative to the machine frame for modifying the given slope setting of said input slope signal means in relation to the rotary position of said working element, whereby said element establishes a planar surface having said predetermined cross slope regardless of the rotary position thereof during travel of said machine.   
     
     
       2. The control system according to claim 1 wherein, said slope sensing unit is mounted in fixed relation to said working element. 
     
     
       3. The control system of claim 1 wherein; said position sensing means is connected with said input slope signal means and adapted to produce a rotational correction signal related to the rotational position of the working element relative to the machine frame, said rotational correction signal being combined with said input slope signal to modify the same prior to being delivered to said slope signal mixing means.   
     
     
       4. The control system according to claim 2 wherein; said position sensing means is connected with said input slope signal means and adapted to produce a rotational correction signal related to the rotational position of the working element relative to the machine frame, said rotational correction signal being combined with said input slope signal to modify the same prior to being delivered to said slope signal mixing means.   
     
     
       5. In a traveling machine having a movable frame, an elongated surface working element supported by said frame, an adjustment means on the machine to adjust the elevation of at least one end of said element relative to said frame, said machine being adapted to establish a planar surface having a predetermined cross slope angle defined as the angle between the surface established and a horizontal plane, said angle being located in a vertical plane perpendicular to the direction of travel of the machine, a control system comprising in combination; 
     
     
       a slope sensing unit operatively associated with said working element and having means to produce a slope signal proportional to the degree of inclination of said element relative to a horizontal plane, input slope signal means providing a constant signal of predetermined value corresponding to the desired slope angle of the working element,   slope signal mixing means adapted to produce a difference signal representing the difference between said input slope signal and said sensed slope signal,   slope control means responsive to said difference signal for controlling said adjustment means for correcting the elevation of said one end of said working element to maintain said desired slope signal, and   position sensing means operatively associated with said working element and responsive to the rotary position of said working element relative to the machine frame for modifying the given slope setting of said input slope signal means in relation to the rotary position of said working element,   whereby said element establishes a planar surface having said predetermined cross slope regardless of the rotary position thereof during travel of said machine.   
     
     
       6. The control system according to claim 5 wherein, said slope sensing unit is mounted in fixed relation to said working element. 
     
     
       7. The control system of claim 5 wherein said position sensing means is connected with said input slope signal means .[.and adapted to produce with said input slope signal means.]. and adapted to produce a rotational correction signal related to the rotational position of the working element relative to the machine frame, said rotational correction signal being combined with said input slope signal to modify the same prior to being delivered to said slope signal mixing means.   
     
     
       8. The control system of claim 6 wherein; said position sensing means is connected with said input slope signal means and adapted to produce a rotational correction signal related to the rotational position of the working element relative to the machine frame, said rotational correction signal being combined with said input slope signal to modify the same prior to being delivered to said slope signal mixing means. .Iadd.9. In a traveling machine having a movable frame, a rotatable frame mounted on the movable frame for rotational movement about a rotatable frame axis perpendicular to a plane defined by the rotatable frame, an elongated surface working element supported on the rotatable frame for rotational movement about said rotatable frame axis, and adjustment means on the machine to adjust the elevation of one end of the working element relative to the other end and to adjust the rotational position of the working element around the rotatable frame axis relative to the movable frame, said machine being adapted to establish a planar surface having a predetermined cross slope angle defined as the angle between the surface established and a horizontal plane, said angle being located in a vertical plane perpendicular to the direction of travel of the machine, a control system comprising in combination;   a slope sensing unit for producing a sensed slope signal indicative of the degree of inclination of said working element relative to a horizontal plane,   mounting means for mechanically mounting said slope sensing unit for direct movement with said working element,   rotary position sensing means connected between said rotatable frame and said movable frame for producing a rotary position signal indicative of the rotational position of said working element around said rotatable frame axis relative to said movable frame, and   slope control means responsive to said sensed slope signal and said rotary position signal to control said adjustment means with respect to a desired working element slope angle in a manner to maintain the cross slope angle of the established surface constant, whereby the adjustment means will automatically modify the slope of the working element as the working element is rotated about the rotatable frame axis to maintain constant the   
     
     
        cross slope of the established surface. .Iaddend..Iadd.10.  The control system according to claim 9 wherein said slope control means includes; input slope signal means providing a constant input slope signal of predetermined value corresponding to the desired angle of the working element; and   first signal mixing means for producing a first difference signal representing the difference between said input slope signal and said sensed sloped signal. .Iaddend..Iadd.11. The control system according to claim 9, further including;   grade sensing and control means connected with said working element and said adjustment means for sensing a preset grade datum and maintaining one end of said working element at a predetermined elevation related to said grade datum during travel of the machine. .Iaddend..Iadd.12. The control system according to claim 11, wherein said grade sensing means is adapted to follow said preset grade datum and to provide a grade signal related to deviation of said one end of the working element from the preset datum,   input grade signal means providing a constant signal of predetermined value corresponding to the desired elevation of said one end of the working element,   grade signal mixing means for producing a difference signal representing the difference between said input grade signal and said sensed grade signal, and   grade control means responsive to said difference signal for controlling said adjustment means for correcting the elevation of said one end of the working element. .Iaddend..Iadd.13. The control system according to claim 10 wherein said input slope single means and said rotary position sensing means are operatively connected such that said constant input slope signal is modified by said rotary position signal before being supplied to said first signal mixing means. .Iaddend..Iadd.14. The control system according to claim 13, further including;   grade sensing and control means connected with said working element and said adjustment means for sensing a preset grade datum and maintaining one end of said working element at a predetermined elevation related to said grade datum during travel of the machine. .Iaddend.