Dual Cylinders For Effecting Tilt And Pitch Functions Of A Dozer Blade

Abstract

A bulldozer blade is coupled to the forward ends of right and left push-beams of a push frame by pivotal connections defining a transverse axis about which pitch adjustments of the blade pitch may be made by right and left push-beam cylinders provided between the beams and blade, the cylinders also effecting tilt adjustments of the blade about a longitudinal axis located midway between the push-beams. The push frame is, mounted for pivoting vertically about a second transverse axis so as to adjust the height of the blade, with a pair of lift cylinders being coupled between the bulldozer and the blade for effecting this adjustment. An electro-hydraulic control system including an electronic controller is provided for effecting individual or simultaneous control of the push-beam cylinders for effecting blade tilt and pitch adjustments in accordance with operator inputs, with, position feedback being provided by cylinder position sensors.

The invention claimed is: 
     
         1 . A work vehicle, comprising:
 a track machine comprising an operator input unit, the operator input unit. configured to sense a pitch input and a tilt input and to generate a pitch signal in response to the pitch input and a tilt signal in response to the tilt input,   a blade,   a push frame including fore-and-aft extending, right and left push beams coupled to the track machine, and said blade being mounted to a front of said push frame;   a hydraulic circuit comprising hydraulic right and, left push beam cylinders respectively having first ends coupled to right and left end regions of said blade and second ends coupled to said right and left push beams, the right and left push beam cylinders being operative for tilting and pitching the blade relative to the push frame respectively about a fore-and-aft extending tilt axis and a transversely extending pitch axis, electro-hydraulic first and second directional control valves being respectively fluid-coupled for controlling the flow of fluid to the right and left push beam cylinders from a source of fluid pressure, and for controlling the flow of fluid from the right and left push beam cylinders to a sump;   first and second position sensors respectively associated with the right and left push beam cylinders and being operative for sensing and generating first and second position signals respectively representative the strokes of the right and left push beam cylinders; and   an electrical controller coupled for receiving said first and second position signals from each of said first and second position sensors, and coupled for sending a command signal to each of said first and second directional control valves; electro-hydraulic to the first and second position sensors and the hydraulic circuit, the controller configured to:   receive the pitch signal, the tilt signal, the first position signal, and the second position signal,   determine a first valve position and a second valve position, each of the first and second valve commands dependent on the pitch and tilt inputs and the first and second lengths, and   output a first control signal commanding the first valve to the first valve position and a second control signal commanding the second valve to the second valve position.   
     
     
         2 . The work vehicle, as defined in  claim 1 , and further including right and left lift cylinders respectively coupled between said work vehicle and right and left end regions of said blade; and right and left lift cylinder position sensors for sensing, the position of, and generating respective right and left lift cylinder position signals representing the positions of the right and left lift cylinders; said right and left lift cylinder position sensors being coupled to said controller; and said controller having a memory containing a table of geometric relationships and being responsive to the right and left lift cylinder position signals for generating a signal representative of the change in pitch occasioned by operation of the lift cylinders; and said controller being responsive to said signal representative of the change in pitch occasioned by operation of the lift cylinders to effect operation of said right and left push beam cylinders to compensate for the pitch change brought about by operation of the lift cylinders. 
     
     
         3 . In combination:
 a propelling vehicle;   a dozer blade;   a push frame including right and left push beams having respective front ends pivotally connected to lower rear locations of said dozer blade by first couplings defining a transverse blade pivot axis, and having respective rear ends pivotally connected to opposite sides of said propelling vehicle by second couplings defining a transverse arm pivot axis;   right and left push-beam cylinders respectively coupled between the right and left push-beams and the blade and being operative for selectively effecting changes in blade pitch by pivoting the blade about said blade pivot axis, and said right and left push-beam cylinders also being operative for selectively effecting tilting of said blade about a longitudinal axis located halfway between said push-beams;   an electro-magnetically controlled first direction control valve being coupled to said right push-beam cylinder and to a source of fluid pressure and a sump, and being selectively shiftable for effecting extension and, retraction of said first direction control valve;   an electro-magnetically controlled second direction control valve being coupled to said left push-beam cylinder and to the source of fluid pressure and to the sump and being selectively shiftable for effecting extension and retraction of said left push-beam cylinder;   a control system for controlling operation of said first and second direction control valves for controlling said right and left push-beam cylinders by selectively shifting said first and second direction control valves, the control system including:   operator tilt and pitch input devices respectively operable for generating tilt and pitch input signals;   an electronic controller coupled for receiving said tilt and pitch input signals from said tilt and pitch input devices, and coupled for sending pitch and tilt output signals to each of said first and second control valves; manually operated tilt and pitch input devices coupled to said electronic controller for providing tilt and pitch input signals to said electronic controller, with said tilt and pitch input devices being simultaneously operable, if desired, for effecting a blended tilt and pitch input command signal to be sent to said electronic controller which operates in response to the blended tilt and pitch input command signal to send a blended output command signal to said first and second direction control valves for causing said right and left push-beam cylinders to be actuated for causing the tilt and pitch of the blade to be simultaneously adjusted.   
     
     
         4 . The bulldozer, as defined in  claim 3 , wherein said electronic controller includes a memory containing a table relating blade position to various stroke conditions of the right and left push-beam cylinders; and right and left push-beam cylinder position sensors being respectively associated with said right and left push- beam cylinders and operative for providing right and left push-beam position signals to said electronic controller which determines a current position of the blade and compares it to the commanded position of the blade determined from the pitch and/or tilt input signals. 
     
     
         5 . The bulldozer, as defined in  claim 4 , and further including at least one lift cylinder coupled to the blade; and
 a lift cylinder position sensor being associated with said at least one lift cylinder and operable for providing a lift cylinder position signal to said electronic controller, which determines, from said table of geometric relationships, any change necessary to be made in the pitch command signal in view of the pitch of the blade resulting from the position of the push-beams about said second transverse axis.