Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Specified load or strain transmission device from specimen...
Reexamination Certificate
1999-03-29
2001-11-13
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Specified load or strain transmission device from specimen...
Reexamination Certificate
active
06314818
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to an apparatus and method of measuring the stress on a work machine and, more particularly, to an apparatus and method that determines whether the stress is greater than a pre-determined stress limit value and responsively stores a value of the stress in memory and provides an associated message to the operator.
BACKGROUND ART
Work machines having an attached implement, such as motor graders, excavators, mining shovels, backhoe loaders, wheel loaders, track type tractors, wheeled tractors, compactors, track type loaders, and the like, are used for moving earth. Such implements may include buckets, blades, impact rock rippers, and other material handling apparatus. Typically, work machines may be configured to perform various work cycles. For example, a track type loader typically has a bucket used to dig, collect (rack) a load, carry a load, and/or dump a load.
In general, a work machine has a frame and an implement having a linkage operably connecting the implement to the frame. Typically, as the work machine performs various work cycles, various portions of the frame, implement, and linkage can be subject to structural or mechanical stress. Such work cycles may include digging, loading, racking, lifting, carrying, dumping, and lowering a load. Often the stress repeatedly occurs on particular structures or portions of the machine. The stress can cause fatigue or damage to the structures. Structural portions most susceptible to stress are cross members, and more particularly, portions of the cross members proximate to the weldjoint.
Tension strain gauges and compression strain gauges secured to beams and connected in a Wheatstone bridge circuit to deliver an output signal related to the magnitude of force supported by the beams is known from U.S. Pat. No. 4,420,985.
Further, it is known from U.S. Pat. No. 3,853,001 to use strain gauges mounted within the hinge pin of a crane for measuring the force tending to overturn a crane and immediately indicate the measurement to the operator on a single gauge irrespective of the angle of the boom.
Accordingly, the art has sought an apparatus and method of measuring the stress on a work machine which: records the highest stress corresponding to abnormal usage; signals all the overloads directly to the operator; helps the operator reduce the wear and damage to structural members; and is more economical to manufacture and use.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention, a work machine adapted to be controlled by an operator and for acting upon a load through a plurality of work cycles is provided. The work machine includes a frame, a plurality of ground engaging devices supporting the frame, an operator compartment supported by the ground engaging devices, an implement having a linkage for operably connecting the implement to the frame, an engine operably coupled to the ground engaging devices, and a stress measurement control system. The stress measurement control system includes a strain gauge sensor assembly, a memory, an electronic controller, and an operator interface. The strain gauge sensor assembly is mounted to the frame or the implement and is adapted to provide a stress signal having a value indicative of the stress acting upon the frame or the implement. The memory is adapted to store a stress signal value and a pre-determined stress limit value. The electronic controller is associated with the memory and is adapted to receive the stress signal and the pre-determined stress limit value. Further, the electronic controller determines whether the stress signal value is greater than the pre-determined stress limit value and responsibly stores the stress signal value in the memory and provides an associated message. The operator interface is adapted to receive the associated message and provides the message to the operator in the operator compartment.
In another aspect of the present invention, a method for measuring the stress on a work machine adapted to be controlled by an operator and for acting upon a load through a plurality of work cycles is provided. A strain gauge sensor assembly is mounted to the frame or the implement and a stress signal having a value indicative of the stress acting upon the frame or the implement is provided. The stress signal value and a pre-determined stress limit value is stored. The stress signal and the pre-determined stress limit value are received and it is determined whether the stress signal value is greater than the stress limit value. In response, the stress signal value is stored and an associated message is provided to the operator in the operator compartment.
These and other aspects and advantages of the present invention will become apparent to those skilled in the art upon reading the detailed description of the best mode for carrying out the invention in connection with the drawings and appended claims.
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Buck Byron G.
Caterpillar Inc.
Davis Octavia
Fuller Benjamin R.
Meyers Liza J.
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