Window pane electric heating system - has automatic switch, disconnecting panes from electric network in case of pane breakage

摘要

The heating system uses electric conductors on the pane(s) periphery. The heating current is interrupted during breakage of the glass pane by an automatic switching device (23) which separates the glass panes (S1-S6) from the mains completely in such instance. The switch pref. contains a bistable starting relay, in front of which is series-connected a comparator and a transistor. The bistable relay can be reset only by a reset pushbutton for exclusively manual operation. The automatic switch may be allocated to several window panes. If the window panes are also used for heat insulation, they may be coated with a conductive heating layer. The switching device discerns between mains failures and a defective glass pane. The system can be used with advantage in refrigeration and deep freezing installations for windows affording inspection despite greater temperature differences.