many of the fastening , connection , processes and other means and components utilized in this invention are widely known and used in the field of the invention described , and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art , and they will not therefore be discussed in significant detail . also , any reference herein to the terms “ left ” or “ right ” are used as a matter of mere convenience , and are determined by standing at the rear of the machine facing in its normal direction of travel . furthermore , the various components shown or described herein for any specific application of this invention can be varied or altered as anticipated by this invention and the practice of a specific application of any element may already by widely known or used in the art by persons skilled in the art and each will likewise not therefore be discussed in significant detail . fig1 shows the present invention utilized in connection with a self - propelled windrower 10 ; however , it will be appreciated that the principles of the present invention are not limited to a self - propelled windrower , or to any specific type of harvesting machine . in the illustrated embodiment , the self - propelled windrower 10 comprises a tractor 12 and a header 14 , the header 14 being attached to the front end of a frame 18 or chassis of the tractor 12 . the header may be of generally any suitable construction and design , and will include crop - harvesting mechanisms , such as a sickle cutter 20 . header 14 additionally includes a reel 24 rotatable at a fixed or variable speed , as denoted by arrow a , for directing crops toward header 14 for harvesting by sickle cutter 20 . a draper 26 comprising endless belts is disposed and operable for directing the harvested crop toward the center of header 14 . sickle cutter 20 of header 14 includes a row of knives extending sidewardly across the lower front of header 14 and reciprocally driven in the sideward direction , by at least one drive 34 which preferably includes a fluid motor 36 . fluid motor 36 is connected in fluid communication with a pto 38 of tractor 12 , by fluid lines 40 and 42 , for receiving pressurized fluid therefrom , for powering the reciprocating movement of the sickle knives , in the well known manner . reel 24 and draper 26 can also be fluid driven , reel 24 by another fluid pto , and draper 26 also by pto 38 . header 14 is removably mountable on a pair of lower arms which extend forwardly from frame 18 of tractor 12 , and which are movable upwardly and downwardly for positioning the header at a desired cutting height , or at an elevated transport position , using one or more lift cylinders ( not shown ), also in the well known manner . the upper end of the header is connected to frame 18 by an upper or center link connected to a mechanism operable for tilting the header to a desired orientation , again , in the well known manner . a typical operating speed for sickle 20 , will be about 1800 cycles per minute . because header will be interchangeable on windrower 10 with other headers , and receive pressurized fluid from and are controlled by pto 38 , as noted above , it is desirable to have a capability to calibrate the output of pto 38 with the output of the header for optimizing header performance , and for providing a capability for adjusting to changing conditions , particularly changing engine speed . pto 38 includes a pto driveline 50 including a fluid valve arrangement 52 controllably operable for directing pressurized fluid through fluid lines 40 and 42 as desired or required for powering a header , such as header 14 or header 16 , connected to windrower 10 . referring also to fig2 , which is a schematic of pto driveline 50 , the flow of pressurized fluid to valve arrangement 52 is generated by a variable displacement pump 66 , the displacement of which is determined by the angle of an internal swash plate , the angle being controlled by a header pto forward / reverse solenoid 54 . in another embodiment , the pump can be a fixed displacement pump operated by a header pto forward solenoid 56 and a header pto reverse solenoid 58 . solenoid 54 is controlled by an electrical signal , the electrical current value of which can be very precisely controllably varied through a range between zero and a greater amount . pto driveline 50 includes a programmable control module 60 connected to header pto forward / reverse solenoid 54 by suitable conductive paths 62 , which can be , for instance , wires of a wiring harness . control module 60 is preferably a conventionally constructed and operable microprocessor based tractor control module , or the like , suitably located on tractor 12 , such as in an operator cab 64 . pump 66 is driven by an engine 68 of tractor 12 , in the well known manner . pump 66 is operable for providing fluid pressurized to predetermined system pressure by operation of engine 68 at at least a low idle speed , which is about 900 rpm . other pertinent elements of pto driveline 50 include a header pto switch 70 selectably operable by an operator for selecting a forward or reverse direction of operation of the pto ; a header speed switch 72 selectably operable by an operator for increasing or decreasing the speed of operation of the header ; a header pto emergency stop switch 74 ; a seat switch 76 ; and a display device 78 , which can be , for instance , an interactive touch screen device or the like which can be automatically adapted or turned on for receiving operator inputs , each of switches 70 , 72 , 74 and 76 , and device 78 , being located in operator cab 64 and connected to the control module 60 via suitable conductive paths 62 . electrical power is provided in the normal manner from an electrical system of the tractor , as represented by the + 12 v connections in the schematic . other aspects of windrower 10 include a propulsion driveline including fluid motors in connection , respectively , with drive wheels , which are differentially operated for effecting steering movements . the differential operation of the fluid motors of the driveline , as well as the travel speed , is effected by varying the displacement of fluid pumps in connection with the respective fluid motors of the driveline . a typical range of operating speeds of engine 68 of windrower 10 will be from about 1300 rpm , which represents a low speed , to about 2200 or 2300 rpm , which represents a typical normal operating speed . because pump 66 of pto driveline 50 is driven by engine 68 , operation of engine 68 at different speeds will result in operation of pump 66 at different speeds . this will cause pump 66 to generate different fluid flow outputs as the speed of the engine changes , if the displacement of the pump is not correspondingly adjusted for maintaining a particular fluid flow level . when a header 14 is installed , if an amount of fluid flow in excess of that required for operating the header is generated by pto 38 , the excess flow will be directed through a diverter or pressure relief valve to tank . this is inefficient , as the generation of the excess flow requires engine power , and the fluid is unnecessarily heated , thereby subjecting it and related componentry to heat related problems , which is undesirable . as noted above , as an alternative , it would be desirable to have an automatic capability to determine an optimal fluid flow for operating a header 14 installed on windrower 10 , then to maintain that optimal fluid flow , regardless of variations in engine speed , that is , to provide a capability to vary the displacement of pump 66 as the speed of engine 68 changes , in a manner for maintaining optimal or near optimal fluid flow conditions . referring also to fig3 and 3 a , a flow diagram 80 illustrating steps of a method of the instant invention for calibrating pto 38 for operation with a header , such as header 14 , is shown , for determining the control signals for providing a desired level of fluid flow to the header at any of a predetermined number or range of engine operating speeds . the steps of flow diagram 80 are preferably programmed in and executable by control module 60 at appropriate times , such as , but not limited to , when a header 14 is first installed , or after a repair or service affecting stored register values . when the operator invokes a calibration , or re - calibration , control module 60 will output a message on the screen of display device 78 that calibration is initiating , and request an action by the operator to enable the header 14 , via the two action pto switch 74 . at block 82 control module 60 initiates the calibration routine . at block 84 , control module 60 sets the engine speed at one of a plurality of predetermined engine speeds . a first variable , being the electrical current range , is initialized to 16 ma as denoted by block 85 . with the engine at the selected speed , control module 60 applies or outputs an initial control signal to solenoid 54 having a predetermined initial signal value within a predetermined signal range for the engine speed , as denoted at block 86 . control module 60 then monitors the resulting header speed , as denoted at block 91 . as denoted at decision blocked 92 , control module 60 then compares the operating speed of the header resulting from the outputted initial control signal to a predetermined target speed value for the header , here , which is preferably 725 rpm . control module 60 will determine if the speed is greater than the target value , as denoted at decision block 92 . if yes , control module 60 will follow balloon b to proceed to calculate an incrementally changed control signal value , as denoted at block 93 , and following balloon a to block 87 , and output or apply the changed signal value to the pump solenoid 54 . if no , control module 60 will proceed following balloon c to calculate an incrementally changed control signal value , as denoted at block 94 , and output or apply the changed signal value to the pump solenoid 54 . following balloon a , the electrical current range is then divided in half , as denoted by block 87 . the electrical current range is then compared to the minimum electrical current resolution required , 0 . 5 ma as denoted by decision block 88 . the process then repeats , starting at block 91 until the electrical current range is less than the minimum electrical current range resolution , 0 . 5 ma , as denoted by decision block 88 . when the minimum electrical current range resolution requirement is met , the electrical current value , corresponding to a header speed of 725 rpm at the present commanded engine speed , is stored as denoted by block 98 . control module 60 then proceeds to determine if the signal map is complete , as denoted at decision block 89 . if not , control module 60 will proceed to set the engine speed at the next incremental value , as denoted at block 95 . additionally , the electrical current range is re - initialized to 8 ma , as denoted by block 96 , and the present electrical current value is reduced by 2 ma , as denoted by block 97 . the process then continues , starting at block 91 until the full range of engine speeds are mapped , at which time the process concludes when the engine speed is equal to 2100 rpm , as denoted in decision block 89 . control module 60 will preferably utilize a binary tree algorithm to increment or decrement , respectively , the control signal value so as to move the resultant header speed toward the target value , such that successive increments or decrements will be halved , and the header speed will be progressively moved toward the target value , until it is reached . as a result of execution of the calibration routines of the instant invention , registers of control module 60 will contain information representative of the electrical current values required to be directed to solenoid 54 for providing fluid flow for effecting operation of header 14 at the target operating speed thereof . these values can then be used by control module 60 , for determining new current values for achieving pump swash plate angles required for providing the optimal fluid flow to the header for a variety of engine speeds , such that flow diverted to tank by the diverter or pressure relief valve , and the attendant problems associated with it , are minimalized . referring also to fig4 - 28 , lines of code of an actual computer program embodying the above described steps of the method of the invention is disclosed . the notes accompanying the lines of code describe many features of the method of the invention . it will be understood that changes in the details , materials , steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention . the foregoing description illustrates the preferred embodiment of the invention ; however , concepts , as based upon the description , may be employed in other embodiments without departing from the scope of the inventions . accordingly , the following claims are intended to protect the invention broadly as well as in the specific form shown .
an apparatus and method for calibrating a pto for driving a header of an agricultural windrower , wherein a programmable control module in connection with at least signal operated device in operative control of a variable displacement pump operable for controlling operation of the pto , is programmed as part of an automatic calibration routine for determining values for the control signals required for operating the header at a predetermined target speed for a plurality or range of speeds of an engine driving the pump , such at the pump can be controlled to minimize occurrences of overpumping of fluid and resultant problems .