A two chamber system with fill gas in one chamber and vacuum in the other provides a means of burning in one or more vacuum tubes while avoiding contamination from environmental gases. Vacuum tubes are often burned in after being sealed. Some processes burn-in the tubes before sealing them. The burn in process can take days and provide ample opportunity for environmental gases to contaminate the vacuum tube. The vacuum tube's fill tube passes through the vacuum chamber and into the fill gas chamber. Environmental gases leaking past the fill tube are evacuated by the vacuum. Similarly, fill gas leaking past the fill tube is also evacuated to vacuum. As such, the environmental gases are drawn away before contaminating the vacuum tube.

TECHNICAL FIELD

Embodiments relate to the manufacture of flame detector tubes and vacuum tubes. Embodiments also relate to sputtering, gettering, vacuum chambers, manifolds, and process gas delivery systems.

BACKGROUND OF THE INVENTION

Vacuum tubes, the predecessors of transistors and diodes, are air tight chambers with cathodes and anodes. The air is largely evacuated from the tube, hence the name vacuum tube. The tube's cathode is held at a lower voltage than the tube's anode so that electrons are accelerated from the cathode to the anode. As electrons move to the anode, they collide with air molecules knocking even more electrons loose and thereby amplifying the number of electrons. In many tubes, the cathode is heated to produce thermionic electrons. In other tubes, photons are allowed to impact the cathode to cause the release of photoelectrons.

Vacuum tubes are rarely used in circuitry any more. They are, however, often used in light detection. Some tubes are so sensitive that a single photon can cause an electron to leave the cathode and induce a large avalanche of secondary and tertiary electrons that reach the anode. One type of photon sensitive tube is a flame detector tube. A flame detector tube is sensitive to the photons produced by flames.

In operation, a tube's anode and cathode are subjected to a constant and necessary bombardment of electrons and ions. The result is the etching and sputtering of the cathode and anode. To provide long tube life, the anode and cathode are often made from or coated with resistant materials such as tungsten and molybdenum while still being consistent with the demands for the proper work function. Similarly, the gas in the tube is chosen to be one that will not damage the anodes and cathodes too much nor react with other tube materials consistent with proper breakdown characteristics. Neon and a neon/hydrogen mix are often used as tube gasses because they are fairly light and nonreactive.

In the manufacture of vacuum tubes, a burn-in period is often required. When first produced, anodes and cathodes are rough. The rough surfaces affect the electric fields and result in inconsistent and occasionally even damaging electron flows and sputtering effects. Burn-in is a process in which the tube is run at an elevated voltage to sputter the surfaces smooth. The materials and gases used in vacuum tubes, however, are specifically chosen to minimize sputtering. Engineering decisions for extended tube life also cause long burn-in times. Some burn-in procedures must be performed before the vacuum tube is sealed. As such, there is ample opportunity for environmental gases to contaminate the inside of the vacuum tube. Systems and methods for contamination free burn-in of non-sealed vacuum tubes are needed.

BRIEF SUMMARY

It is therefore an aspect of the embodiments that a burn-in manifold has a first chamber, a cavity, and a lid. The lid covers the cavity to form a second chamber. An interior wall is shared by the first chamber and the second chamber.

It is also an aspect of the embodiments that the interior wall has an interior wall opening and that the lid has an exterior opening. A vacuum tube's fill tube can reach into the first chamber by passing through the exterior opening, through the second chamber and through the interior wall opening. An exterior seal can seal the fill tube to the exterior wall to prevent environmental gas from entering the second chamber. An interior seal can seal the fill tube to the interior wall to prevent gas from passing from the first chamber into the second chamber. O rings can be used as interior seals and as exterior seals.

DETAILED DESCRIPTION

The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. In general, the figures are not to scale.

A two chamber system with fill gas in one chamber and vacuum in the other provides a means of burning in one or more vacuum tubes while avoiding contamination from environmental gases. Vacuum tubes are often burned-in after being sealed. Some processes burn-in the tubes before sealing them. The burn-in process can take days and provide ample opportunity for environmental gases to contaminate the vacuum tube. The vacuum tube's fill tube passes through the vacuum chamber and into the fill gas chamber. Environmental gases leaking past the fill tube are evacuated by the vacuum. Similarly, fill gas leaking past the fill tube is also evacuated to vacuum. As such, the environmental gases are drawn away before contaminating the vacuum tube.

FIG. 1illustrates a burn-in manifold with a lid107in accordance with aspects of the embodiments. The lid107has exterior openings105, burn-in connectors106, exterior seals104, and a gasket108. The exterior seals can be O-rings that rest in cups115. A manifold body has a cavity112and a first chamber113separated by an interior wall116. The interior wall has interior wall openings114as well as seals104and cups115. Spacer rings109,110can press the seals104against the interior wall116and lid107. A ported spacer ring110has ports111passing from the spacer ring's center to its exterior. A vacuum port118can be connected to a vacuum source while a fill port117can be connected to a gas source. A vacuum tube119has a body101, fill tube103and tube connectors102.

FIG. 2illustrates a burn-in manifold with a lid107and installed vacuum tubes201,202in accordance with aspects of the embodiments. The burn-in manifold ofFIG. 2is the same as that ofFIG. 1with the exception that the lid107and spacer rings are installed. Vacuum tubes201have been pressed through the exterior openings, through the spacer rings, through the interior openings, and into the first chamber. A fill gas in the first chamber113will pass into the vacuum tubes201. Fill gas leaking through the interior openings will be evacuated out the vacuum port118and will not pass into the outside atmosphere. Similarly, environmental gases leaking through the exterior openings will be evacuated to vacuum and will not enter the first chamber113. This is particularly important because otherwise a single bad seal could contaminate every vacuum tube. The vacuum tubes201have their tube connectors102mated to the lid's burn-in connectors. As such, the tubes can be burned-in.

One vacuum tube202is illustrated as pressed into a ported spacer ring. The fill tube is exposed to vacuum such that environmental gas is evacuated from the vacuum tube and out the vacuum port118.

The interior seals and exterior seals minimize the leakage of gases, but can not be trusted to completely prevent all leakage for the entire time that the vacuum tubes burn-in. A burn-in manifold designed for a single tube at a time benefits from the dual chamber arrangement because otherwise it would depend on a single seal and no vacuum evacuation. The dual chamber arrangement is particularly advantageous for a multiple tube manifold such as those illustrated. The reason is a single chamber manifold system contaminates all the vacuum tubes when a single seal fails. Furthermore, single seal failures can easily occur during an entire burn-in cycle. The dual chamber arrangement is resistant to contamination because it is designed to work properly in spite of less than perfect seals.

FIG. 3illustrates a burn-in manifold300in accordance with aspects of the embodiments. The burn-in manifold ofFIG. 3is the same as that ofFIG. 2with the exception of having no lid. Instead of a lid, the burn-in manifold300has a permanent exterior wall301. Like the lid, the exterior wall301has exterior openings, seals, and cups.

FIG. 4illustrates a burn-in manifold lid107in accordance with aspects of the embodiments. The lid107has a gasket108, exterior openings105, seals104, cups115, and gasket108.

FIG. 5illustrates a burn-in manifold cavity in accordance with aspects of the embodiments. The cavity112is surrounded by cavity walls501with the interior wall116forming the cavity112bottom. The interior wall116has interior openings114, seals104, cups115, and gasket108.

FIG. 6illustrates a cut view of a lid600with recessed cups601in accordance with aspects of the embodiments. As with the lids in other figures, the lid600has exterior openings105, a gasket108, and seals104. A recessed cup601can hold a seal104such as on O-rinq and can be less expensive to produce.

FIG. 7illustrates high level flow diagram of using a burn-in manifold in accordance with aspects of the embodiments. After the start701a burn-in manifold is obtained702and vacuum tubes are obtained703. The vacuum tubes' fill tubes are pressed through the manifolds exterior openings such that they reach into the spacer rings but not into the interior openings705. The second chamber is evacuated705which also evacuates the vacuum tubes. The fill tubes are then pressed through the interior openings such that the tube connectors and burn-in connectors mate706. Fill gas is passed into the first chamber such that the vacuum tubes are filled707and then the vacuum tubes are burned-in708. The burn-in process is done709and the vacuum tubes can be sealed and packaged for sale.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows.