| 摘要 |
<p>Plastic extrusions and similar materials are cut off to length using a shear cutter electrically driven and swinging about an axis parallel to the material which is moved by operating a switch after each cut. The cutter blade is fixed to the shaft of a DC motor which operates in steps, each step being one revolution; the speed of revolution is measured and signalled, pref. by a generator; the motor and speed indicator are connected to an electronic control set for given speeds, which compare the motor acceleration, after cutting, with a nominal value and which stops acceleration beyond that value. An induction switch is positioned at 150 deg. on the arc described by the cutter in front of the cutting point; as the cutter approaches this switch feeds a current to set the position of rest of the cutter; a second similar switch on the arc beyond the cutting point changes the polarity of supply to the motor as the cutter passes and hence produces a braking effect. Efficient operation is provided as machine is suitable for mass prodn. and therefore at low costs, minimal mechanical loads and wear on parts, minimal noise level in operation.</p> |
