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US 5,178,808 AGranted
End seal manufacture for ceramic arc tubes
OwnerFrank B. Makar, George A. Fryburginventors
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Abstract
An end plug for an arc tube for a high pressure discharge lamp is made by pressing alumina powder in a tapered cylindrical die so that the diameter of the as-pressed plug is greatest at that part of the plug that has the lowest as-pressed density. The variation in diameter of the as-pressed plug compensates for the variation in density so that upon high temperature sintering, the plug shrinks to a substantially uniform diameter.
Claims4
In the manufacture of an arc tube for an arc discharge lamp, the steps comprising:
- providing pressing apparatus consisting of a tapered cylindrical die closed at one end by a removable anvil and having a close fitting punch at the other end, the die being tapered so that its largest diameter is at the anvil end;
- filling the die with alumina powder;
- pressing the powder into the shape of an end plug;
- removing the as-pressed end plug from the die at the anvil end;
- pressing alumina powder into the shape of an open ended arc tube, the as-pressed arc tube having a lower density than that of the as-pressed end plug;
- inserting an end plug into each end of the arc tube;
- and sintering the arc tube-end plug assembly at a high enough temperature to form a vacuum-tight monolithic seal between the end plugs and the arc tube.
4 more elements
Dependencies are inferred from the claim text.