> > US 4,213,663 1980 RCA >
> This would be RCA Lancaster (I was there several times in the late 1960s) > near Thermacore. > Positive Ion Bombardment of the Cathode could shake out Metastable > Negative Muons. Literature I've had for over 54 years shows/quotes > uncertainty on it being O2- or Cl- Ions. IOW it has never been resolved. > > Fred > > " In accordance with the novel method, as shown in the sole FIGURE, > shortly after the bulb leaves the panel-sealing lehr, and while it is still > hot (about 200.degree. C.) from the lehr, the inside of the bulb is > flushed with wet CO.sub.2 (carbon dioxide) gas. Wet CO.sub.2 gas may be > produced by bubbling CO.sub.2 gas from a cylinder of compressed CO.sub.2gas > through deionized water. When prepared by this method, the gas has a dew > point of about room temperature ( 22.degree. C.). However, the dew point > of the CO.sub.2 gas may be as low as about 0.degree. C. and as high as > 100.degree. C. provided moisture does not condense in the bulb during or > after flushing with the CO.sub.2 gas. Also, while it is preferred that the > temperature of the bulb is higher than about 50.degree. C. (in order to > avoid condensation of moisture) when it is flushed with wet CO.sub.2, the > bulb may be warm, cool or cold. The rate of flushing may be in the range > from about 0.5 CFM (cubic feet per minute) to about 5 CFM, and the time > period of flushing may be in the range from about 0.5 minute to about 5 > minutes. Generally, the smaller the tube, the lower the flushing rate and/or > the shorter the flushing time. > > Flushing may be done by the method shown, for example, in FIGS. 2 to 4 of > U.S. Pat. No. 3,658,401 to J. A. Files, by inserting an elongated tube and > a surrounding resilient stopper into the open end of the neck of the bulb > and admitting the gas from a gas source through a valve and associated > tubing. The upper end of the elongated tube may be formed with apertures for > directing the gas in a desired manner; for example, outwardly. The outer > periphery of the stopper is either noncircular or is formed with > longitudinal grooves or holes to permit the residual gases within the bulb > to be driven out by the gas that is introduced. Instead of centering the > elongated tube axially with respect to the stopper, the elongated tube may > be eccentric to the stopper to improve the flushing action. The sizes of the > elongated tube and the tubing, the sizes of the apertures and the grooves, > and the gas pressure used to introduce the gas are chosen to provide the > desired flushing action within the desired flushing time. In one apparatus > that has been used successfully in making twenty-one-inch rectangular color > picture tubes, the bulb is flushed at the rate of about 2 cubic feet per > minute for about 2 minutes, and the volume within the bulb is exchanged at > least six times. > > After the flushing with wet CO.sub.2 gas is completed, the flushing > apparatus is removed. The inside of the bulb is now flushed in the same > manner as described above with a dry noncontaminating gas, preferably warm > air having a dew point of about - 22.degree. F. The dry noncontaminating > gas used for flushing is preferably dry warn air containing about 350 ppm > water vapor (which has a dew point of about -22.degree. F. or -30.degree. > C.). The flushing gas should be nonreactive to the tube structure. Air, > oxygen, nitrogen, argon, helium, neon, and mixtures thereof may be used. The > water-vapor content of the gas should be less than 1,000 ppm or have a dew > point of less than about - 4.degree. F., Hydrocarbon gases, carbon > dioxide, and other contaminants, if any, should be removed from the flushing > gas. The temperature of the flushing gas is not critical and may be at, > above, or below room temperature. After flushing with dry gas, a resilient > cap, such as that shown in FIG. 5 of the above-cited Files patent, may be > applied to cover the neck opening to maintain the bulb assembly filled with > the dry noncontaminating gas at atmospheric pressure for a relatively long > term prior to the next manufacturing operation, which is usually the > mount-sealing step. It has been found that envelopes so flushed and capped > can be held or stored for several weeks, if necessary or desired, without > substantial degradation of the screen structure. > > The bulb may pass to the next operation without capping, or, if it has > been capped, the cap is removed. Then, the mount assembly is inserted in the > neck of the bulb and the glass stem of the mount assembly sealed into the > neck by known methods; for example, as described in U.S. Pat. No. > 3,807,006 to J. F. Segro et al. The bulb with the mount assembly sealed > therein may now be exhausted and baked to remove gases therein and to degas > various of the structures and internal surfaces, by any known method; for > example, as described in U.S. Pat. No. 2,532,315 to A. L. Johnson et al. > After exhausting and baking the bulb assembly, the tube is completed by > performing the conventional steps of activating the cathode, tipping off the > exhaust tubulation, flashing the getter, aging the cathodes, and testing the > tube. > >
