Abstract:
Row unit lift structure includes electrohydraulic proportional valves connected to an electronic controller which receives inputs from a manual raise/lower switch, a rate response potentiometer, and height control potentiometers in the cab. Signals are also received from row unit height sensing transducers, a tachometer and shaft rotation sensors. When the units are lowered and operational, the controller compares the signals from the height sensing transducers with the signals from the height control potentiometers and sends an electrical control signal to the proportional valves to maintain a selected row unit height. The magnitude of the control signal and thus the rate of correction of height are determined by the rate response potentiometer and the amount of variation between the actual and desired row unit height.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to agricultural harvesters and, more specifically, to a height control for harvester row units. 
     BACKGROUND OF THE INVENTION 
     Harvesters such as cotton pickers include row units supported for vertical movement by lift arms controlled by hydraulic lift cylinders. Extension and retraction of the lift cylinders is controlled by spool valves connected to height sensing skids on the row units, such as shown in commonly assigned U.S. Pat. No. 5,519,988. Electrohydraulic valves provide an on/off function for oil flow to and from the cylinders. During field operations with the electrohydraulic valves in the on position, the skids mechanically move the spools to extend the cylinders when any unit is too low and retract the cylinders when all the units are too far above the surface of the field. 
     Present systems of the type shown in the aforementioned patent have complex hydraulic plumbing which is difficult and time-consuming to connect and maintain. In addition, adjustments of the operating height to provide efficient picking and prevent grounding are relatively difficult. System sensitivity and response time are not easily changed since linkage and internal hydraulic revisions are required. Maintaining good reliability and stability with the complex plumbing systems and mechanical linkages has been a continuing problem. 
     BRIEF SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an improved height control system for a harvester row unit. It is a further object to provide such a unit which overcomes most or all of the aforementioned problems. 
     It is a further object to provide such an improved harvester row unit height control system with simplified and more reliable hydraulic plumbing compared to at least most available systems. 
     It is another object to provide such a harvester height control system which is less expensive and more reliable than most systems. It is still another object to provide such a system which has improved sensitivity and adjustability. 
     It is yet another object of the invention to provide a row unit height control system for a cotton harvester having improved reliability, sensitivity and adjustability. It is a further object to provide such a system which is less complex and costly than many previously available cotton harvester height control systems. 
     The improved hydraulic lift and height control system for a harvester includes electrohydraulic proportional valves to eliminate linkage-actuated valves. A single set of proportional valves connected to height control cylinders and to a controller provides manual or automatic harvester row unit height control. The controller receives inputs from a manual raise/lower switch, a rate response potentiometer, and height control potentiometers in the cab. Signals are also received from row unit height sensing transducers, a tachometer and shaft monitor. The operator actuates the raise/lower switch, which is conveniently located on the hydro control handle, to control extension and retraction of cylinders for movement of the row units between a raised transport position and a lowered field operating position. In the lowered position, the controller compares the signals from the height sensing transducers with the signals from the height control potentiometers and sends an electrical control signal to the proportional valves to maintain the row units at the height selected by the operator. The magnitude of the control signal and thus the rate of correction of height are determined by the rate response potentiometer and the amount of variation between the actual and desired row unit height. The controller prevents automatic operation if the relay to engage the row units is not turned on, and lowering of the row units is inhibited if the tachometer signal indicates the engine is not running. 
     The hydraulic control circuit includes a first proportional valve connected between a source of hydraulic fluid under pressure and the base end of a single acting cylinder to control cylinder extension for raising a set of row units, and a second proportional valve connected between the base end of the cylinder and a return to sump line to control cylinder retraction for lowering the set of row units. A low leakage, electrically controlled on-off valve is connected in series with a second proportional valve and has a normally closed position to prevent unwanted row unit lowering. The controller is connected to the on-off valve and provides a signal for turning the valve on for normal harvester operation. 
     These and other objects, features and advantages of the present invention will become apparent to one skilled in the art upon reading the following detailed description in view of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a cotton harvester having row units supported by a lift assembly. 
     FIG. 2 is a schematic representation of the height control system utilized with the cotton harvester of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, therein is shown a cotton harvester  10  including a main frame  12  supported for forward movement over a field of plants to be harvested by forward drive wheels  14  and rear steerable wheels  16 . A cab  18  is located at the forward end of the main frame  12 . Transversely spaced multiple row harvesting units  20  are supported from the forward end of the frame  12  by hydraulically controlled lift structures  22 . As shown in FIG. 2, two lift frames or structures  22 L and  22 R are provided for supporting two sets of row units  20  on the left- and right-hand sides of the harvester  10 . The row units  20  remove cotton from rows of the plants, and an air duct system  26  directs the removed cotton rearwardly and upwardly into a basket  28 . Although the row units  20  are shown mounted on a self-propelled harvester, it is to be understood that they can also be attached to a tractor in a conventional tractor mounted configuration. 
     Each of the row units  20  includes a forward frame assembly  30  supporting stalk lifter structure  32  which helps to guide adjacent rows of plants into the unit. A height sensing shoe assembly  40  is supported from the frame assembly  30  and controls the lift control structure  22 , as described in further detail below, to maintain the unit  20  at a generally constant height above the ground during field operations as ground and surface conditions vary. 
     Referring to FIG. 2, therein is shown the height control system utilized with the harvester  10  of FIG.  1 . The system provides row unit lift and lower functions and maintains a plurality of the row units  20  at the desired height above the ground to facilitate efficient crop removal and prevent grounding of the forward portion of the units during harvesting operations. Left- and right-hand cylinders  50  and  52 , shown as single acting cylinders in FIG. 2, have base ends pivotally connected to the frame  12  and rod ends connected to conventional left- and right-hand row unit support frames. Typically, one to three row units  20  are supported by each of the support frames, and each row unit  20  includes a height sensing shoe assembly  40 . An electronically controlled hydraulic circuit indicated generally at  58  and connected to a source of hydraulic fluid  59  provides hydraulic fluid flow to and from the cylinders  50  and  52  to raise and lower the units  20  between field working and transport positions and to control the height of the units while in the field working position. 
     Each shoe assembly  40  includes a ground sensor skid  60  having an end  62  pivotally connected to the row unit  20 . A transducer  66  having a rotational axis  66   a  is supported on the unit  20  and includes a radially extending transducer arm  68 . A link  70  connects the end of the arm  68  with a central portion  72  of the skid  60 . The transducer  66  is preferably a hall effect sensor or other non-contact sensor which varies the electrical signal as the transducer arm  68  rotates about the axis  66   a  to provide a height signal dependent upon the height of the row unit  20  above the surface of the ground. Alternatively, the transducer  66  may be a variable resistor or other contact device. An adjustable position device  80  (broken lines of FIG.  2 ), including a cable  82  extending between the device  80  and an adjusting device  84  in the cab  18 , allows an operator to conveniently vary the set point of the transducer  66  on-the-go from the cab as crop and field conditions change so that the transducer signal for a given row unit height can be changed for optimum performance. 
     The output of each transducer  66  is connected to an input of a controller  90  by a line  92 . The controller  90  polls each of the lines  92  for the row units  20  on one row unit lift frame and calculates a correction signal for that frame based on the signals on the line. If the signal from the lowest row unit  20  drops a preselected amount from the desired signal for the preselected height, indicating the unit is too low, the controller  90  will cause the frame to lift so that unit will be farther from the ground. Similarly, if the signals from all of the row units  20  are greater than a predetermined amount from signals for the preselected height, indicating that the units are too high, the controller  90  will cause the frame to lower so that the units will be closer to the ground. 
     A manual lift and lower control  94  located on a hydro control handle  95  in the cab  18  is connected by lines  96  to the input of the controller  90 . Left raise and right raise buttons are provided which can be individually operated if desired to raise either the left or right side of the header. Located on a console  98  of the cab  18  are left- and right-hand height controls  100  and  102  and a response rate control  104  connected to the input of the controller  90  by lines  110 , 112  and  114 . A bus connection indicated at  116  to a shaft monitor and tachometer provides engine and row unit operational status signals to the controller  90  and facilitates communication between the controller and the tachometer when the tachometer is used as a diagnostic display in the cab  18 . 
     The controller  90  includes conventional microprocessor based circuitry which compares the height signals from the transducers  66  on the lines  92  with the desired height set by the controls  100  and  102 . If the actual detected height varies more than a preselected amount from the selected height, the controller  90  signals the hydraulic control circuit  58  to make the necessary change to reduce the variation. The rate of the correction is determined by the setting of the control  104 . 
     The controller  90  polls the connection  116  to determine if the engine on the harvester  10  is running, and, if not, valve operation is prevented. Also, the controller  90  determines whether or not the row units  20  are operating by checking the status of a unit enable relay (not shown) for the units  20  via connection  116  and prevents operation in the automatic height control mode when the relay is not enabled. 
     The hydraulic control circuit  58  includes check valves  124  and  126  connected between the cylinder lines  54  and  56  and electrohydraulic proportional valves  130  and  132 . The valves  130  and  132  have inputs connected to a pressure line  134  connected to the source  59 . The cylinder lines  54  and  56  are also connected to a return line  136  through electrohydraulic check valves  140  and  142  and electrohydraulic proportional valves  144  and  146 . The valves  130 , 132 , and  140 - 146  have control inputs connected by lines  151 - 153  and  161 - 163  to the output of the controller  90 . Since the control structure and description of operation for each of the lift structures  22 L and  22 R is generally the same, only that for the structure  22 L will be described in detail below. 
     When the proportional valve  130  receives a lift signal from the controller  90  via line  151 , the valve moves from the blocking position shown to the regulated flow position wherein the rate of fluid flow through the valve is determined by the signal level from the controller  90 . The fluid flows from the pressure line  134  through the check valve  124  and into the base end of the cylinder  50  to extend the cylinder and raise the left-hand units  20 . The valve  140 , which is a normally closed, very low leakage blocking valve preventing retraction of the cylinder  50  when the harvester  10  is not operating, is activated whenever the automatic height control system is operational. While the cylinder  50  is extending, the controller  90  maintains valve  144  in the blocking position to prevent return flow to the line  136  through the open valve  144 . 
     When the controller  90  detects that the manual control  94  is in the raise position, the valve  130  is moved to the fully open position for fast header lift. To move the header down from the transport position to the field working position, the operator moves the manual control  94  to the lower position. The row units  20  are moved downwardly until they reach the preselected operating heights. When the system is in an automatic height control mode, the controller  90  compares the height signals on the lines  92  with the desired height signal on line  110  set by the operator using the height control  100 . If the units  20  start to drop below the desired range, the controller provides a signal on the line  151  to open the valve  130  and extend the cylinder  50 . The valve  144  remains closed to prevent return flow to the return line  136 . If the amount of deviation between actual and desired row unit height is small, the controller  90  provides a relatively low level of signal on the line  151  to slowly raise the units  20  until the signals on the lines  92  indicates the units are in the desired height range. However, if the difference between the actual and desired height is large, the valve  130  is opened further to assure that the units  20  are lifted quickly to prevent grounding of the units. 
     For retraction of the cylinder  50  to lower the units  20 , the controller  90  signals the valve  144  via line  153  to move from the normal blocking position to the regulated flow position and signals the valve  130  via line  151  to the blocking position (shown). The cylinder  50  retracts at a rate dependent on the signal level from the controller  90  on the line  153 . 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.