伐木造材手段の相違が作業負担におよぼす影響について : 手鋸, チェンソー, ツリー・フェラーの比較

Abstract

作業中の作業者の心拍数を指標にして, 手鋸, チェンソー, ツリー・フェラーという3つの伐木造材手段を比較し, 手段が変われば作業者の負担の程度や負担の質がどのように変化するかを検討し, さらにそれ等変化に応じた研究方向は今後どのようであるべきかについても論じた。比較の結果, チェンソーは手鋸と較べて作業時間を大巾に短縮し, それだけ作業負担を軽減させたが, 作業自体の強さは依然として高いままであったのに対し, ツリー・フェラーは作業の抜本的変革をもたらし, 作業時間のみならず作業自体の強度をも著しく軽減せしめることが明らかになった。しかしツリー・フェラーの導入は, 筋的労働を軽くする反面, 精神的負担を作業者に荷するものであり, この方面の研究と対策が必要であろうが, 精神的負担等に対してR. M. R. やエネルギー消費量に較べて心拍数は敏感に反応しうるので, 心拍数はかかる考察の有効な方法となりうるであろうと推察した。

On the basis of changes of heart-rate of operators, the three methods of felling and bucking--hand-saw, chain-saw, and tree-feller--were compared in order to determine the range and change in quality of operation loads for each method. The following became clear upon comparison: In the operation with chain-saws, the time of operation was considerably curtailed and accordingly the operation load reduced compared with hand-saws (the total heart-rate increase declined by approximately one-sixth to one-tenth), but the level of operation still remained high even with chain-saws. On the other hand, the introduction of the tree-feller represented a drastic change in the felling method, and brought not only reduction in operation times but also remarkable reduction in the level of operation (the rate of increase of heart-rate was 57-67% lower than in the operation using chainsaws). But, while the muscular labour definitely decreases with the introduction of the treefeller, the mental load of the operators can often increase. Further investigation of the mental load of forest operators is necessary, according to the introduction of machines in the forestry. It was proved in this paper that heart-rate was more sensitive to the mental load of operators than R.M.R. and Energy Consumption. So, we can say that it is effective to use heart-rate the investigations of the mental load.