Patent ID: 7511406

Claim:
In a 400 watt metal halide arc discharge lamp having a lamp envelope subject to failure upon impaction from glass shards having a given mass; an arc tube mounted within said envelope, said arc tube having an outside diameter OD; a shard-producing shroud surrounding said arc tube; electrical lead-ins for supplying electrical energy to said arc tube; and a chemical fill within said arc tube to produce light when an arc is formed within said arc tube; the improvement comprising: said shroud having a given thickness T equal to 1.5 mm and a given inside diameter ID, said ID of said shroud being greater than said OD of said arc tube by at least 3 mm and having a relationship such that ID/T is less than 22, whereby any shards produced by said shroud in the event of a non-passive arc tube burst have a mass less than said given mass.