Equipment cutting rigid foam slabs, employs optical, mechanical or electronic detection of cutting stroke, to increase power supplied for rapid action, afterwards reducing it to idling level

摘要

A controller (22) adjusts the hot wire power supply between two non-zero values, for cutting and idling respectively. Preferred features: Switching between power levels is automatic. The change over is governed by the electrical resistance of the heating wire. That part of the wire (18) extending across the cutting path is connected in series with a reference section (19). Together these form one half of a complete bridge circuit, the voltage across a diagonal forming the control signal to switch the controller. Ends of the reference and heating sections are located on a common component electrically connected to the controller. Reference- and heating sections are of the same material. A light beam, on being broken, causes switching to high power, at the start of the cutting stroke. The optical axis is angled with respect to the heating wire. The heater is connected to one component, which is mounted to move with respect to the holder (10). A spring tensions it. A switch on the holder, causes the power change over. The heating wire has a temperature/resistance coefficient of at least 0.01%/ deg K.