Device for controlling a gas-air mixture for a gas flame treatment

A gas flame treatment apparatus for a gas flame pretreatment of plastic surfaces by increasing the surface energy of the surfaces to be treated with a control device for regulation of a gas/air mixture comprising:

• at least one burner (12),
• an air supply duct (13) having a valve (21) that regulates a flow of air,
• a gas supply duct (14) having a valve (41) that regulates a flow of gas,
• a flow measuring device (22) for said air duct,
• a flow measuring device (42) for said gas duct,
• a mixing path (15) of a gas/air mixture leading to said burner (12),
• a regulator (26) for control of said air regulating valve (21),
• a regulator (46) for control of said gas regulating valve (41),
• a central computing unit (28) that, in dependence on reference values for said gas/air mixture and on a reference value for output of said burner (12), outputs at least one control variable to said air regulating valve and said gas regulation valve,
• said control variables being compared in said air regulator and said gas regulator (26, 46) with actual values determined by said flow measuring device (22) for said air supply duct (13) and said flow measuring device (42) for said gas supply duct (14),
• said control variables output by said regulators (26, 46) being adjustable on closed-loop control systems formed by said regulating valves, said flow measuring devices and said regulators,
• said flow measuring devices (22, 42) comprising thermoanemometers separated from said at least one burner (12), and
• a gas/air mixture with a pressure of less than 200 mbar being supplied to said burner (12).