Patent ID: 7026569

Claim:
A control system for controlling the shielding gas supply of an automatic welding apparatus, which automatic welding apparatus has a continuous electrode feed device having a feed signal output which is indicative of a continuous electrode feeding speed (U), which automatic welding apparatus is connected to a gas tank via a gas supply line, in which supply line there may according to choice be arranged a pressure regulator and a manometer characterised in that the control system comprises a controllable gas flow valve having a valve gas inlet, a valve gas outlet and a valve control signal input for receiving a valve control signal; a gas flow sensor having a gas inlet, a gas outlet and a sensor signal output; and a programmable control circuit having a first and a second input and a first output; wherein the gas tank has an inlet connection to the valve gas inlet, the valve gas outlet has a valve outlet connection to the gas inlet, the gas outlet has a gas outlet connection to a shielding gas outlet, the feed signal output has a feed signal connection to the first input, the sensor signal output has a sensor signal connection to the second input, the first output has a control signal connection to the valve control signal input, the programmable control circuit comprises a processor which, in accordance with at least one program in a first memory in the control circuit, and on the basis of signals received at the first and second inputs, provides at the first output the valve control signal, which provided valve control signal is adjustable by means of the programmable control circuit within a dynamic range of values limited in accordance with a predetermined minimum gas flow (Qmin) through the valve and a predetermined maximum gas flow (Qmax) through the valve, and the program comprises at least one instruction to the processor instructing the processor to issue at the first output a signal that is constant and having a value which corresponds substantially to the minimum gas flow (Qmin) through the valve from the time the signal at the first input exceeds a first threshold value (Uth1) and in an immediately subsequent first predetermined time period.