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Really? I was under the impression that the glass isn't a fully enclosed "bulb" so to speak, but is cut off at one end to accommodate the rest of the necessary
by devindotcom 5y ago
Really? I was under the impression that the glass isn't a fully enclosed "bulb" so to speak, but is cut off at one end to accommodate the rest of the necessary hardware, and glue completes the seal. Perhaps you're right. I can't seem to find a diagram or anything that shows this, though.
- xenadu02 5y agoThe leads are inserted through a glob of hot glass, along with a glass tube. The bulb's open base is heated to make it soft, the blob containing the leads with attached filament are inserted, then the base is welded to the lead blob. Last the tube is used to evacuate the bulb and/or inject inert gasses. While under this vacuum the tube is melted and smashed closed, permanently sealing the bulb. Attachment of the base comes later.
- MisterTea 5y agoIf you examine a clear incandescent bulb, you will see that the support for the filament is hollow and has a tube inside extending down. This little "straw" is the point of connection for evacuation where the air is removed and then back-filled with argon. The argon coaxes the tungsten back onto the filament preventing rapid sputtering which would happen in a pure vacuum. After the argon the little tube is heated until it hits melting point and crimped off for a near perfect hermetic seal. The argon pressure is still well below atmosphere so the bulb is still considered under "vacuum" compared to atmosphere.