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.