Studies on the Bush Cutter equipped with a Fixed Blade (3)

To assess the degree of safety to the machine operators, we checked into the conditions of cut grass and pebbles scattered in operation of two types of bush cutter, one the cutter with a specially designed fixed (stationary) blade and the other an ordinary blade of 8-tooth and nylon wire. The major results obtained are summarized as follows.1) After mowing Digitaria adscendens Henr. in the experiment, were checked into the traces of cut pieces of the grass and the grass juice left on the operator's clothes. In the use of nylon wire cutter, which cuts the grass with centrifugal force, the traces were conspicous on the operator's waist and below. In 30 minute operation, operator's right and left knees accounted for about 80% of the entire area of the traces(trace area of cut objects cm2/100cm2). In the use of the cutter with a fixed blade and an ordinary 8-tooth blade, scattering of the cut grass was less. Scattering was much less (ratio of trace area 0.1%) with the fixed blade cutter which is designed to reduce the rotating speed of the cutter blade to about 1/3 of that of an ordinary blade.2) Scattering of ceramic triangular pyramids (DIN specification) from the fixed blade cutter was less than that of an ordinary 8-tooth blade. The result is due to the lower rotating speed of the cutter blade of the former cutter and also to the crushed objects being contained or being prevented from scattering by the fixed blade.3) Scattering direction tended to be in the left side of the operator with all of the fixed blade cutter, an ordinary 8-tooth blade and nylon wire cutter. Scattering density number of scattered objects in the operator's position with the fixed blade cutter was down to half (1/2) of that of an ordinary 8-tooth blade and nylon wire cutter.4) Scattering height with the fixed blade cutter and an ordinary 8-tooth blade cutter was less than 50cm. Scattering density at each designated height in the operator's position was lower for the fixed blade cutter than that of an ordinary 8-tooth blade cutter which leads us to determine that the danger from scattered objects decreases in using the former type of the machine.