Excavating – Road grader-type – Condition responsive
Reexamination Certificate
1999-12-09
2001-10-02
Shackelford, H. (Department: 3671)
Excavating
Road grader-type
Condition responsive
C091S033000, C172S004500
Reexamination Certificate
active
06295746
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to manual and automatic positioning of a work implement and, more particularly, to a method and apparatus for controlling manual and automatic movement of a work implement of a work machine.
BACKGROUND ART
Work machines, such as motor graders, dozers, compactors, pavers, profilers and scrapers, are used for geographic surface altering operations. The machines include a work implement, such as a surface altering blade, that is movably connected to a frame of the machine by one or more hydraulic motors or cylinders, or the work implement may be fixed to the machine frame. The position of the blade relative to the work surface must be accurately controlled to achieve the desired surface altering cut.
In motor graders, for example, the surface altering blade is movably connected to the grader frame by a pair of independently actuatable hydraulic lift cylinders that are mounted on either side of the machine frame. The hydraulic lift cylinders are independently extensible and retractable to move corresponding sides of the blade relative to the machine frame. Each side of the blade may be set by the operator to operate in either a “manual” or “automatic” mode of operation.
In the “manual” mode, the operator controls the elevational position of one or both sides of the blade through a pair of control levers mounted in the cab of the grader. Each control lever modulates a corresponding manual control valve connected to that lever. The pair of manual control valves are connected between a hydraulic fluid supply and a corresponding one of the hydraulic lift cylinders. The operator modulates the manual control valves to achieve the desired elevational position of the blade on the manually controlled side of the blade.
A pair of electrically actuatable control valves are also connected between the hydraulic fluid supply and a corresponding one of the hydraulic lift cylinders. The electrically actuatable control valves receive command signals from an implement controller to adjust the elevational position of one or both sides of the blade assigned to the “automatic” mode of operation.
During a grading operation, an operator may desire to adjust the elevational position of one side of the blade by modulating the manual control valve corresponding to each side of the blade. However, if the blade side to be adjusted is assigned to the “automatic” mode of operation, the operator's modulation of the manual control valve may contend with automatic operation of the automatic control valve on that side of the blade when both valves are operated simultaneously. When this occurs, the operator's input to the manual control valve may be resisted, and the desired adjustment in the blade's elevational position may not be achieved. Moreover, simultaneous operation of the manual and automatic control valves on the same side of the blade results in performance and reliability degradation of the motor grader's implement control system.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
The present invention overcomes the foregoing and other shortcomings and drawbacks of work implement positioning systems and methods heretofore known. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
In one aspect of the invention, an apparatus for controlling movement of a work implement of a work machine having a hydraulic pump and a hydraulic motor for actuating the work implement is provided. A work implement positioning device, such as a manually actuatable control lever, is movable by an operator for directing movement of the work implement in a “manual” mode of operation. A manually actuatable control valve is connected to the work implement positioning device, and is further connected between the hydraulic pump and the hydraulic motor. The manual control valve controls operation of the hydraulic motor in the “manual” mode of operation.
An electrically actuatable control valve is connected between the hydraulic pump and the hydraulic motor for controlling operation of the hydraulic motor in an “automatic” mode of operation. An implement controller is coupled to the electrically actuatable control valve for actuating the electrically actuatable control valve in the “automatic” mode.
A pressure sensing device is operatively connected to the manually actuatable control valve, and is further coupled to the implement controller. The pressure sensing device is responsive to hydraulic pressure within the manually actuatable control valve resulting from movement of the work implement positioning device. Upon operator modulation of the work implement positioning device, the pressure sensing device is operable to apply a signal to the implement controller for altering operation of the electrically actuatable control valve in the “automatic” mode. The implement controller may disable the “automatic mode” of the electrically actuatable control valve upon operator modulation of the manual control valve.
Advantageously, the pressure sensing device associated with the manual control valve eliminates contention between the manual control valve and the automatic control valve during control of the work implement, and reduces performance and reliability degradation of the implement control system when the manual and automatic control valves are actuated simultaneously.
In another aspect of the present invention, a method for controlling movement of a work implement of a work machine having a hydraulic pump and a hydraulic motor for actuating the work implement is provided. A manual control valve is connected between the hydraulic pump and the hydraulic motor for controlling operation of the hydraulic motor in a “manual” mode of operation. An electrically actuatable control valve is connected between the hydraulic pump and the hydraulic motor for controlling operation of the hydraulic motor in an “automatic” mode of operation. An implement controller is connected to the electrically actuatable control valve for actuating the electrically actuatable control valve in the automatic “mode”. Hydraulic pressure within the manually actuatable valve is monitored, and a signal is applied from the manually actuatable control valve to the implement controller indicating hydraulic pressure within the manually actuatable control valve resulting from movement of the work implement positioning device for altering operation of the electrically actuatable control valve in the “automatic” mode.
REFERENCES:
patent: 4179981 (1979-12-01), Yeou
patent: 4934463 (1990-06-01), Ishida et al.
patent: 5551518 (1996-09-01), Stratton
patent: 5647439 (1997-07-01), Burdick et al.
Meduna Gregory L.
Slunder Jeffrey L.
Burrows J. W.
Caterpillar Inc.
Derry Thomas L.
Shackelford H.
Wood Herron & Evans LLP
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