| 摘要 |
In a flashback arrestor unit for welding equipment or the like, a heat-sensitive valve, through which gas is supplied and which operates in the event of substantial or prolonged overheating of the equipment, comprises a permanent magnet (44) and a valve closure (38, 34, 36) of magnetically susceptible material acted upon by a spring (40) which is normally overcome by the force of attraction of the magnet on the valve closure, thereby to keep the valve open. In the event of overheating which causes the valve closure to lose magnetic susceptibility, the spring (40) is free to urge the valve closure against a valve seat in order to close the valve and shut off the gas supply. The valve closure may be formed by two discs (34, 38) and an intervening spaces (36). An aperture (46) in the disc (34) provides a controlled relief of the pressure differential across the disc, thus delaying reopening of the valve, following cooling of the unit. <IMAGE> |
