Abstract
In hilly and mountainous areas many looped-handle type weed cutters are used for clearing weeds in the levee of paddy fields. This type of weed cutter is light, cheap, and can take free working postures. For this type of weed cutter, which we call the holding type, working strain is large because the cutter is entirely supported by both hands. Therefore, we have developed the method of hanging a weed cutter by two rubber ropes from shoulder belts attached to a back-mounted board, such as has been used in the conventional shoulder type weed cutter. We call this method the “two shoulder belts” type. In this paper, we have studied how to estimate the magnitude of reduction in working strain caused by the two shoulder belts type of weed cutter.
The results are as follows;
1) It was proved that the rate of increase in heart rate was inversely proportional to the reduction in working rate (h/10a).
2) It may be possible to estimate the magnitude of the reduction in working strain by comparing the approximate curves of exponential function in the required working time of 2-5h/10a of the same worker.
3) Compared with the holding type, the two shoulder belts type decreased the working strain by about 10% of the ratio of increase in heart rate.
The two shoulder belts type weed cutter may reduce working strain to approximately that of a conventional shoulder type weed cutter with a rubber hanger-rope.
The above-mentioned results make it clear that the two shoulder belts type can decrease the working strain without spoiling the free working postures in the holding type.
