Plasma welding pistol with water cooling circuit - where electricity flows only while water travels through drain from pistol

摘要

Plasma welding appts. with a coolant circuit contg. a pressure switch between the coolant supply and the welding pistol, so that electric current only flows to the pistol when the pressure of the coolant actuates the switch. The novelty is that monitoring devices are provided in the coolant circuit downstream of the pistol to cut off the electricity if the outlet flow of the coolant stops or drops to a small amt. The monitoring element pref. consists of a switch located in the drain from the pistol and which cuts off the electricity when the coolant flow through the drain drops below a min. amt., esp. using a switch operated by capacitance and steering a relay. Although the pressure switch prevents the supply of electricity when coolant pressure is absent, it does not cut off the supply if a blockage occurs and no coolant leaves the pistol, i.e. producing damage. The invention ensures that electricity is only supplied while coolant is flowing out of the pistol.