Research of protection equipment for the load cell receiving a large impact load

A load cell does not usually break as long as it is used within its fatigue limit range. However, eccentric loads or impact loads applied to the load cell could sometimes cause unexpectedly large stress; and if such excessive stress is repeatedly exerted upon it, it results in fatigue fracture of the cell. Load cells used on scales in which objects were dropped onto it for weighing had often showed output failures approximately after one year of use. Investigation of the load cells revealed that they had cracks on the upper inside of the spring element. Through analysis of the failure plane, we presumed that the cracks were caused by fatigue resulting from the repeated stress. Naturally, the load cells were incorporated with the stoppers for overload protection. We found from the research process for the cause of the cracks that the scales subject to impact load had some problems with the open/shut mechanism for feeding the weighing objects onto the weighing platform, and the engineering design for the over-load stopper. In this paper, we describe the theoretical analysis and experiments carried out in order to determine the causes of the problems to find out the solutions; how the impact load affects the load cell, as well as how to prevent a similar problem in the future