Patent ID: 7511429

Claim:
An arc tube for use in a high intensity discharge lamp, comprising: an elongated outer envelope defining two opposed ends and an inner cavity therebetween; an electrode sleeve protruding outwardly from each end of the outer envelope, each electrode sleeve having a passageway from outside of the arc tube into the inner cavity; an electrical feedthrough member inserted into the passageway of the electrode sleeve, the feedthrough member including an inner rod that extends into the inner cavity of the arc tube and a ceramic sleeve encircling a portion of the inner rod disposed within the passageway, wherein the electrical feedthrough member further includes a middle rod having one end outside of the electrode sleeve and an opposed distal end joined to the inner rod at a point inside of the electrode sleeve, and an outer rod joined to the middle rod at the end outside of the electrode sleeve; and a sealing compound disposed at an outwardly facing end of the passageway for sealing the feedthrough member to the electrode sleeve, the sealing compound extending into the passageway of the electrode sleeve but spatially separated from the ceramic sleeve.