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A welding helmet is a type of headgear used when performing certain types of welding to protect the eyes, face and neck from flash burn, ultraviolet light, sparks, infrared light, and heat. Most commonly used with arc welding processes such as shielded metal arc welding, gas tungsten arc welding, and gas metal arc welding. Welding helmets are necessary to prevent arc eye, a painful condition where the cornea is inflamed. Welding helmets can also prevent retina burns, which can lead to a loss of vision. Both conditions are caused by unprotected exposure to the highly concentrated ultraviolet and infrared rays emitted by the welding arc.〔(Elvex Safety Products ''How Light Affects the Eye'' )〕 Ultraviolet emissions from the welding arc can also damage uncovered skin, causing a sunburn-like condition in a relatively short period of welding. The modern welding helmet used today was first introduced in 1937 by Willson Products.〔("One Piece Helmet Cut To Protect The Welder ) ''Popular Mechanics'', August 1937 -- bottom-left of page 217〕 Most welding helmets include a window covered with a filter called a lens shade, through which the welder can see to work. In most helmets, the window may be made of tinted glass, tinted plastic, or a variable-density filter made from a pair of polarized lenses. ==Speedglas Auto-Darkening Filters== In 1981, a Swedish manufacturer named Hornell introduced the Speedglas Auto-Darkening Filter, an LCD electronic shutter that darkens automatically when sensors detect the bright welding arc.〔(3M Speedglas Auto-Darkening Welding Helmet )〕 With such electronic auto-darkening helmets, the welder no longer has to get ready to weld and then nod their head to lower the helmet over their face. The advantage of an Auto-Darkening Filter (ADF) versus a traditional passive filter is that the welder does not need to adjust the position of welding helmet manually which not only saves time but also reduces the risk of exposure to the extremely bright and harmful light generated by the welding process. In January 2004, 3M acquired all assets of Hornell, including the Speedglas auto darkening helmets brand name and patents. Speedglas helmets are now sold by 3M.〔(3m.com )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Welding helmet」の詳細全文を読む スポンサード リンク
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