Abstract:
A ripper depth limit system and method that includes a lift input for operator controls to raise and lower the ripper, a depth limit input, a lift sensor input that senses the ripper lift cylinder position, and a controller that processes the inputs to generate, execute and revise ripper lift cylinder commands that keep the ripper above the ripper depth limit. The depth limit input can select the ripper depth limit from a plurality of predefined depth limits, or between minimum and maximum ripper depths, or by some other method. The ripper depth limit system can also include a pitch input for operator controls of ripper pitch, and a pitch sensor that senses ripper pitch cylinder position, and the controller can process the pitch inputs to generate, execute and revise ripper pitch and lift cylinder commands that keep the ripper above the ripper depth limit.

Description:
FIELD OF THE INVENTION 
     This present invention generally relates to an automatic control system for a ripper used on construction equipment, and more specifically to automatically controlling ripper depth. 
     BACKGROUND OF THE INVENTION 
     Typically a ripper mounted on construction equipment such as a tractor is manually controlled by the operator who raises or lowers the ripper shank or varies the ripper pitch based upon experience, ground conditions, vehicle speed and other working conditions. Ripper depth is typically adjusted by removing a pin from the ripper shank and repositioning the shank relative to the ripper carrier and reinserting the pin. This effectively changes the length and potential depth of the ripper. This naturally requires operator time to reposition the ripper using the pin, and requires considerable skill and experience on the part of the operator to determine the desired depth to minimize the changes that need to be made to ripper length. 
     SUMMARY 
     A system is disclosed that limits the depth of a ripper mounted to a tractor by electronically sensing the lift cylinder length and limiting that length in order to limit the depth of ripper engagement with the ground. 
     A ripper depth limit system is disclosed for a ripper that includes a ripper lift cylinder. The ripper depth limit system includes an operator lift input, an operator ripper depth limit input, a lift cylinder sensor coupled to the ripper lift cylinder and a ripper electro-hydraulic controller. The operator lift input generates an operator lift signal that controls the raising and lowering of the ripper. The operator ripper depth limit input sets a ripper depth limit. The lift cylinder sensor senses the position of the ripper lift cylinder and generates a lift cylinder position signal. The ripper electro-hydraulic controller processes the operator lift signal, the lift cylinder position signal and the ripper depth limit; and generates and outputs ripper lift cylinder commands that do not allow the ripper depth to exceed the ripper depth limit. The ripper electro-hydraulic controller can include a position processor for determining a ripper position based on the lift cylinder position signal, where the position processor provides the ripper position for further processing by the ripper electro-hydraulic controller. 
     The operator ripper depth limit input can include an activation control for activating the ripper depth limit function, and a depth setting for setting the ripper depth limit. The operator ripper depth limit input can include a selector for selecting the ripper depth limit from a plurality of predefined depth limits. Alternatively, the operator ripper depth limit input can include a selector for selecting the ripper depth limit between a minimum ripper depth and a maximum ripper depth. 
     The ripper lift cylinder commands can be output to a ripper lift spool valve controlling the raising and lowering of the ripper. The ripper lift cylinder commands can be output to an output conditioning processor, and the output conditioning processor can output the conditioned ripper lift cylinder commands to a ripper lift spool valve controlling the raising and lowering of the ripper. 
     The ripper depth limit system can also include an operator pitch input, and a pitch cylinder sensor coupled to a ripper pitch cylinder, where he operator pitch input generates an operator pitch signal for controlling the pitch of the ripper; and the pitch cylinder sensor senses the position of the ripper pitch cylinder and generates a pitch cylinder position signal. The ripper electro-hydraulic controller can also process the operator pitch signal and the pitch cylinder position signal to generate and output ripper pitch cylinder commands that do not allow the ripper depth to exceed the ripper depth limit. The ripper pitch cylinder commands can be output to a ripper pitch spool valve controlling the pitch of the ripper. The ripper pitch cylinder commands can be output to an output conditioning processor that outputs conditioned ripper pitch cylinder commands to a ripper pitch spool valve controlling the pitch of the ripper. The ripper electro-hydraulic controller can include a position processor for determining a ripper position based on the lift and pitch cylinder position signals. 
     A ripper depth limit method is disclosed for controlling a ripper coupled to a lift cylinder that raises and lowers the ripper. The ripper depth limit method includes setting a ripper depth limit, reading a lift cylinder position from a sensor coupled to the lift cylinder, determining a ripper position using the lift cylinder position reading, receiving a ripper lift cylinder command from an operator control device, and determining whether executing the ripper lift cylinder command will cause the ripper to exceed the ripper depth limit. When the ripper lift cylinder command will not cause the ripper to exceed the ripper depth limit, the method includes executing the ripper lift cylinder command. When the ripper lift cylinder command will cause the ripper to exceed the ripper depth limit, the method includes revising the ripper lift cylinder command to not cause the ripper to exceed the ripper depth limit and executing the revised ripper lift cylinder command. The method then includes returning to receive another ripper lift cylinder command. 
     After the determining a ripper position step and before the receiving a ripper lift command step, the ripper depth limit method can include determining whether the ripper position exceeds the ripper depth limit; and when it exceeds the ripper depth limit, generating a ripper lift command to raise the ripper to the ripper depth limit. After the receiving a ripper lift cylinder command step, the ripper depth limit method can include determining whether the ripper depth limit functionality is still activated; and when it is not still activated, executing the ripper lift cylinder command and exiting the ripper depth limit method. 
     Setting a ripper depth limit can include reading one of a plurality of predefined depth limit values from a depth limit selector. Alternatively, setting a ripper depth limit can include determining a position of a selector between a minimum and maximum value, and determining the ripper depth limit based on the position of the selector. 
     A ripper depth limit method is disclosed for controlling a ripper coupled to a lift cylinder that raises and lowers the ripper and a pitch cylinder the controls the pitch of the ripper. The ripper depth limit method includes setting a ripper depth limit, reading a lift cylinder position from a lift sensor coupled to the lift cylinder, reading a pitch cylinder position from a pitch sensor coupled to the pitch cylinder, determining a ripper position using the lift and pitch cylinder position readings, receiving a ripper lift or pitch cylinder command from an operator control device, and determining whether executing the ripper lift or pitch cylinder command will cause the ripper to exceed the ripper depth limit. When the ripper lift or pitch cylinder command will not cause the ripper to exceed the ripper depth limit, the method includes executing the ripper lift or pitch cylinder command. When the ripper lift or pitch cylinder command will cause the ripper to exceed the ripper depth limit, the method includes revising the ripper lift or pitch cylinder command to not cause the ripper to exceed the ripper depth limit and executing the revised ripper lift or pitch cylinder command. The method then includes returning to receive another ripper lift or pitch cylinder command. 
     After the determining a ripper position step and before the receiving a ripper lift or pitch cylinder command step, the ripper depth limit method can include determining whether the ripper position exceeds the ripper depth limit, and when it exceeds the ripper depth limit, generating a ripper lift command to raise the ripper to the ripper depth limit. After the receiving a ripper lift or pitch cylinder command step, the ripper depth limit method can include determining whether the ripper depth limit functionality is still activated, and when it is not still activated, executing the ripper lift or pitch cylinder command and exiting the ripper depth limit method. 
     The step of revising the ripper lift or pitch cylinder command to not cause the ripper to exceed the ripper depth limit can include: for a ripper lift cylinder command, revising the ripper lift cylinder command to lower the ripper to the ripper depth limit only; and for a ripper pitch cylinder command, generating and executing a ripper lift cylinder command to raise the ripper and executing the ripper pitch cylinder command so the ripper does not exceed the ripper depth limit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary embodiment of a ripper coupled to a crawler; 
         FIG. 2  illustrates an exemplary electro-hydraulic (EH) system for controlling a ripper; 
         FIG. 3  illustrates a more detailed view of an exemplary embodiment of the EH controller that can be used in the EH system of  FIG. 2 ; 
         FIG. 4  is a flow diagram of an exemplary control process for a ripper depth limit system that uses sensor readings from the ripper lift cylinder(s); and 
         FIG. 5  is a flow diagram of an exemplary control process for a ripper depth limit system that uses sensor readings from the ripper lift and pitch cylinders. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the novel invention, reference will now be made to the embodiments described herein and illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the novel invention is thereby intended, such alterations and further modifications in the illustrated devices and methods, and such further applications of the principles of the novel invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the novel invention relates. 
     A system is disclosed that limits the depth of a ripper attached to a crawler by electronically sensing the lift cylinder length and limiting that length in order to limit the depth of ripper engagement with the ground. The system can include electro-hydraulic (EH) valves, a microprocessor, an operator input device, and a sensor for sensing the length of at least one of the ripper carrier lift cylinders. When the operator commands a ripper lower function, a limiting function can be used to limit the minimum length of the ripper cylinder to either a predefined or custom defined length which effectively limits the ripper engagement depth. 
       FIG. 1  illustrates an exemplary embodiment of a ripper  110  coupled to a crawler  100 . The ripper  110  includes a shank holder  112 , a ripper shank  114  with a tip  116 , a pair of ripper pitch cylinders  120 , a pair of ripper lift cylinders  130  and a pair of links  140 . The proximal ends of the ripper pitch cylinders  120 , the ripper lift cylinders  130  and the links  140  are coupled to the crawler  100  and the distal ends of the ripper pitch cylinders  120 , the ripper lift cylinders  130  and the links  140  are coupled to the shank holder  112 . The ripper lift cylinders  130  can be extended and retracted to raise and lower the ripper  114 . The pair of ripper pitch cylinders  120  can be extended and retracted to change the pitch of the ripper  114 . The ripper shank  114  can be manually raised or lowered in the shank holder  112 . 
       FIG. 2  illustrates an exemplary electro-hydraulic (EH) system  200  for controlling a ripper. The EH system  200  includes a ripper EH controller  202 , a lift spool valve  250 , a pitch spool valve  260 , a pair of lift cylinders  210 ,  220 , a pair of pitch cylinders  230 ,  240 , a flow source P and a sink. The ripper EH controller  202  receives operator and system inputs and generates output signals to control the spool valves and cylinders. 
     The ripper EH controller  202  receives operator inputs from a ripper lift controller  204 , a ripper pitch controller  206  and a ripper depth limit controller  208 . The ripper lift and pitch controllers  204 ,  206  can be any of various types of controllers known in the art, for example a single joystick for both lift and pitch control, or separate joysticks for each of lift and pitch control. The ripper depth limit controller  208  can also be of various types of controllers, for example a switch, knob, button, menu, etc. The ripper EH controller  202  processes the operator inputs to control the ripper. 
     At least one of the ripper lift cylinders  210 ,  220  has a lift cylinder position sensor  214 . The lift cylinder position sensor  214  senses the position of the piston  212  in the lift cylinder  210  and sends a sensor output to the ripper EH controller  202 . The ripper EH controller  202  can use the output of the lift cylinder position sensor  214  to determine the position of the ripper relative to the main geometry of the tractor. 
     One of the ripper pitch cylinders  230 ,  240  can have a pitch cylinder position sensor  234 . The pitch cylinder position sensor  234  senses the position of the piston  232  in the pitch cylinder  230  and sends a sensor output to the ripper EH controller  202 . The ripper EH controller  202  can use the output of the pitch cylinder position sensor  234  to more accurately determine the position of the ripper relative to the main geometry of the tractor. As shown below, it is optional to include position sensors on the pitch cylinders for the ripper depth limiting system. 
     The ripper EH controller  202  processes the operator and sensor inputs and sends control signals to the lift spool valve  250  and the pitch spool valve  260 . The lift spool valve  250  includes a first movement actuator  252  and a second movement actuator  254  to move the lift spool valve  250  to a desired position. The lift spool valve  250  also includes an input side (bottom) coupled to a flow source P, for example a pump, and an output side (top) coupled to the lift cylinders  210 ,  220 . The first movement actuator  252  can be used to move the lift spool valve  250  to retract the lift cylinders  210 ,  220 . The second movement actuator  254  can be used to move the lift spool valve  250  to extend the lift cylinders  210 ,  220 . 
     The pitch spool valve  260  includes a first movement actuator  262  and a second movement actuator  264  to move the pitch spool valve  260  to a desired position. The pitch spool valve  260  also includes an input side (top) coupled to a flow source P, for example a pump, and an output side (bottom) coupled to the pitch cylinders  230 ,  240 . The first movement actuator  262  can be used to move the pitch spool valve  260  to retract the pitch cylinders  230 ,  240 . The second movement actuator  264  can be used to move the pitch spool valve  260  to extend the pitch cylinders  230 ,  240 . 
       FIG. 3  illustrates a more detailed view of an exemplary embodiment of the ripper EH controller  202 . The ripper EH controller  202  includes a table of geometric relationships  306  which can be used to determine ripper position relative to the tractor based on system parameters including ripper lift and pitch cylinder positions. The inputs from the lift cylinder position sensor  214  and the pitch cylinder position sensor  234  are processed by a cylinder position processor  304  which also uses the table of geometric relationships  306  to determine ripper position data. The ripper position data computed by the position processor  304  is sent to an operator command processor  302  and to a position limiting processor  310 . 
     The operator command processor  302  processes the ripper position data generated by the position processor  304 , along with the inputs from the operator lift and pitch controllers  204 ,  206 , and the table of geometric relationships  306  to generates lift cylinder commands and pitch cylinder commands. The lift and pitch cylinder commands are both sent to the position limiting processor  310 . 
     The input from the ripper depth limit selector  208  is processed by a ripper depth limit processor  308  to generate a ripper depth limit command. The ripper depth limit command generated by the ripper depth limit processor  308  is sent to the position limiting processor  310 . 
     The position limiting processor  310  processes the inputs from the operator command processor  302  and the ripper depth limit processor  308 , and uses the table of geometric relationships  306  to determine lift and pitch cylinder commands to send to an output conditioning processor  312 . If the ripper depth limit option is active, and the operator commands would cause the ripper to exceed the depth limit, then the position limiting processor  310  would modify the ripper lift and pitch commands to execute the operator commands without exceeding the depth limit. 
     The output conditioning processor  312  sends commands from the ripper EH controller  202  to the lift spool valve  250  and the pitch spool valve  260 . The output conditioning processor  312  sends lift commands to the movement actuators  252 ,  254  to position the lift spool valve  250  and control the lift cylinders  210 ,  220 . The output conditioning processor  312  sends pitch commands to the movement actuators  262 ,  264  to position the pitch spool valve  260  and control the pitch cylinders  230 ,  240 . 
       FIG. 4  is a flow diagram of an exemplary implementation of a control process for the ripper depth limit that uses sensor readings from the lift cylinder(s) and not the pitch cylinder(s). When a command is processed, at block  402  the system checks if the ripper depth limit is activated. If the ripper depth limit is activated then control is passed to block  408 , otherwise control is passed to block  404 . At block  404 , the system checks if the command is a lift cylinder command. If the command is a lift cylinder command then control is passed to block  406 , otherwise the system returns to process the next command. At block  406 , the system executes the lift cylinder command and then returns to process the next command. 
     If the ripper depth limit option is activated, then at block  408  the system retrieves and sets the ripper depth limit and then at block  410  the system checks the length of the ripper lift cylinder(s). Then at block  412 , the system checks if the ripper depth limit is exceeded. If the ripper depth limit is exceeded then control is passed to block  414 , otherwise control is passed to block  416 . At block  414 , the system retracts the ripper lift cylinders to raise the ripper to the ripper depth limit, and then passes control to block  416 . 
     At block  416  the system waits for a lift cylinder command. When a lift cylinder command is received, control passes to block  418  where the system checks if the ripper depth limit option is still activated. If the ripper depth limit option is not still activated then at step  406  the lift cylinder command is executed and control is passed back to block  402  to wait for the depth limit option to be activated again. If the ripper depth limit option is still activated then control is passed to block  420 . 
     At block  420  the system determines whether the lift command will lower the ripper beyond the depth limit. If the lift command will not lower the ripper beyond the depth limit then the lift cylinder command is executed at block  422 , and control is passed back to block  416  to wait for the next lift cylinder command. If the lift command would lower the ripper beyond the depth limit then the lift cylinder command is revised at block  424  to only lower the ripper to the depth limit, the revised lift cylinder command is executed at block  422 , and control is passed back to block  416  to wait for the next lift cylinder command. 
       FIG. 5  is a flow diagram of an exemplary implementation of a control process for the ripper depth limit that uses sensor readings from both the lift and pitch cylinders. When a command is processed, at block  502  the system checks if the ripper depth limit is activated. If the ripper depth limit is activated then control is passed to block  508 , otherwise control is passed to block  504 . At block  504 , the system checks if the command is a ripper lift or pitch cylinder command. If the command is a ripper lift or pitch cylinder command then control is passed to block  506 , otherwise the system returns to process the next command. At block  506 , the system executes the ripper lift or pitch cylinder command, and then returns to process the next command. 
     If the ripper depth limit option is activated, then at block  508  the system retrieves and sets the ripper depth limit, then at block  410  the system checks the length of the ripper lift and pitch cylinders, and at block  512  the system determines the ripper depth. Then at block  514 , the system checks if the ripper depth exceeds the ripper depth limit. If the ripper depth limit is exceeded then control is passed to block  516 , otherwise control is passed to block  518 . At block  516 , the system retracts the ripper lift cylinders to raise the ripper to the ripper depth limit, and then passes control to block  518 . 
     At block  518  the system waits for a ripper lift or pitch cylinder command. When a ripper lift or pitch cylinder command is received, control passes to block  520  where the system checks if the ripper depth limit option is still activated. If the ripper depth limit option is not still activated then at step  506  the ripper lift or pitch cylinder command is executed and control is passed back to block  502  to wait for the depth limit option to be activated again. If the ripper depth limit option is still activated then control is passed to block  522 . 
     At block  522  the system determines whether the ripper lift or pitch command will lower the ripper beyond the depth limit. If the ripper lift or pitch command will not lower the ripper beyond the depth limit then the command is executed at block  524 , and control is passed back to block  518  to wait for the next ripper lift or pitch cylinder command. If the ripper lift or pitch command would lower the ripper beyond the depth limit then the command is revised at block  526  to only lower the ripper to the depth limit or raise the ripper to the depth limit if the pitch command would lower the ripper beyond the depth limit. From block  526  control is passed to block  524  where the revised lift or pitch cylinder command is executed, and then control is passed back to block  518  to wait for the next ripper lift or pitch cylinder command. 
     While exemplary embodiments incorporating the principles of the present invention have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.