US 3895709 A
A mercury capsule comprises a mercury-filled metal tube, of measured capacity, having closed ends, each of which includes end portions which are cold welded and resistance welded to form an hermetic seal and intermediate portions, which are crimped closed. The length of the intermediate crimped portions of each capsule is designed to permit the mercury within the capsule to expand and stress the lightly crimped portions, during processing operations of a device in which a capsule is mounted, without opening the hermetically sealed end portions of each capsule.
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Description (OCR text may contain errors)
[ METAL MERCURY CAPSULE  Inventor: George J. Przybylek, Scotch Plains,
Burroughs Corporation, Detroit, Mich.
22 Filed: Apr. 27, 1973 21 Appl. No.: 355,178
 U.S. Cl. 206/84; 313/223; 313/484;  Int. Cl. B65d 81/00; l-lOlj 61/20; HO1j/6l/44  Field of Search 206/84, 498, 525
 References Cited UNITED STATES PATENTS 1,855,760 4/l932 l-lolborn 206/84 X 1,934,369 7/1933 Mendenhall 206/84 X 2,322,421 6/1943 Cox 206/84 X [4 1 July 22, 1975 Primary ExaminerLeonard Summer Attorney, Agent, or Firm-Paul W. Fish; Robert A. Green  ABSTRACT A mercury capsule comprises a mercury-filled metal tube, of measured capacity, having closed ends, each of which includes end portions which are cold welded and resistance welded to form an hermetic seal and intermediate portions, which are crimped closed. The length of the intermediate crimped portions of each capsule is designed to permit the mercury within the capsule to expand and stress the lightly crimped'portions, during processing operations of a device in which a capsule is mounted, without opening the hermetically sealed end portions of each capsule.
2 Claims, 5 Drawing Figures Z/II////T///// PATENTED JUL 2 2 ms Fig.5
METAL MERCURY CAPSULE BACKGROUND OF THE INVENTION For many years,- display devices such as NIXIE tubes have used mercury vapor along with the normal inert gas content to minimize cathode sputtering. A NIXIE tube comprises a relatively large bulb or envelope in which is mounted a stack of glow cathodes in the form of characters. Mercury is usually introduced in such a device from a glass capsule which is disposed within the tube envelope and contains a ball of mercury. To release the mercury, the capsule is heated to cause the mercury to expand and break the glass.
Recently, thin, flat, gas-filled display panels have come into wide use, and these devices also use an inert gas and mercuryvapor. A display panel generally comprises a thin, flat envelope including a base plate and a face plate. The base plate carries various electrodes including groups of glow cathodes, and the face plate carries the associated anodes for the groups of cathodes. The base plate and face plate are sealed together with a close spacing between them. Due to their construction, their gas volume, and the nature of their electrodes, display panels have a relatively strict requirement with respect to the quantity of mercury provided. However, glass capsules cannotbe made in mass production so that they uniformly include the same measured quantity of mercury.
In addition, due to limited space in panel devices, the glass capsule cannot be mounted within the tube envelope, so it is mounted in a glass tubulation secured to the base plate of the panel and communicating with the interior of the panel through a hole in the base plate.
The tubulation is used to evacuate the panel and to introduce, the desired gas filling and mercury vapor. While thisarrangement works well, the tubulation represents an item of expense which is considerable when millions of panels are manufactured, and it complicates processing of panels; In addition, the tubulation is fragile and is easily broken.
Another problem in panels arises from the fact that globules of mercury remain in the tubulation after the glass capsule has been broken and after the desired quantity of mercury vapor has entered the panel itself. Often, such globules enter the panel through the hole in thebase plate when the panel is handled and during shipping. Such globules can cause problems in the panel, forexample, byforming short circuits between closely spaced electrodes.
SUMMARY OF THE INVENTION Briefly, a mercury capsule embodying the invention includes a mercury-containing portion, a lightly closed portion on either side thereof, and hermetically-sealed end portions.
DESCRIPTION OF THE DRAWINGS FIG. 5 is a sectional view of the panel shown in FIG. 4 including a mercury capsule,
DESCRIPTION OF THE PREFERRED EMBODIMENTS A mercury capsule 10 embodying the invention is made of metal and includes a central chamber -12 which is filled with mercury 14. On either side,of the central chamber, the capsule has closed portions 16 made up of lightly crimped portions 50 and, adjacent to portions 50, the ends 40 which are hermetically sealed so that the capsule is gas-tight.
According to the method of: the invention, metal mercury capsules 10 are made from a metal tube 20 (FIG. 2) of titanium, iron, or the like, of generally circular cross-section, and having an outside diameterof about 20 mils and an inside diameter of about 10 mils. Mercury is poured into the tube 20 at one end, and, when the tube is filled, as indicated by the flow of inercury from the opposite end, one end is lightly crimped. Next, light crimps are formed in the wall of the tube at suitable spaced locations 30 along the tube to form individual capsules (FIG. 3), each of which-is completely filled with-a measured quantity. of mercury.
Next, the central portions 31 of the crimped portions .30 of the tube 20 a're ti'ghtly crimped and deformed to, in effectyform a cold weld. This cold welding operation is performed at-such a pressure thata favorable resistance is formed, the resistance 'being optimal for a subsequent resistance welding operation. Those skilled in the art can readily determine the magnitude of pressure required to achieve the required cold weld and resistance. 7 r I Next, the cold welded regions are resistance welded to form hermetic seals which form theends 40 of the individual capsules 10 which are formed when the tube 20 is broken up into the individual capsules 10 in any suitable manner. It is noted that the portion 50 of capsule 10 between the resistance weld seal area 40 and the central mercury-containing portion 12 is the portion which is lightly crimped but is not cold welded or resistance welded, for a purpose to be described.
In using a capsule 10, the capsule is mounted in the envelope of a display panel 68 of the type shown in copending application Ser. No. 173,854, filed Aug. 23, 1971 and now abandoned. A panel of this type, illustrated in FIGS. 4 and 5, includes, briefly, an insulating base plate 70, on which are supported a plurality of groups of cathode glow segments and their associated conductors and other structural elements (not shown). The panel also includes an insulating face plate spaced from and sealed to the base plate and carrying on its inner surface a transparent conductive anode for each group of cathodes 80.
It is noted that the tubulation 92 (shown in dash lines) normally used in such panels and secured to the base plate, is not required in panel 68.
In one suitable arrangement, the capsule 10 is mounted at one end of the panel between the base plate 70 and face plate 90 and in close, heat-receiving relationship to the seal area between the base plate and face plate. The capsule is secured in place in any suitable manner. During the processing of the panel, relatively high temperatures are used, particularly during the making of the hermetic seal between the base plate and face plate which comprise the envelope of the display panel. During the sealing operation, the heat which is applied causes the mercury in the capsule to expand. Because of the capsule construction, the expanding mercury can open the lightly crimped portions 50, if necessary; however, it does not affect the hermetically sealed end portions 40. At a desired time in the processing of the panel, a laser beam is used to drill a small hole in the capsule 10 to permit mercury vapor to escape therefrom into the gas atmosphere of the panel.
A mercury capsule, according to the invention, used for providing mercury in display panels used in calculators, is of the order of 0.4 inch in overall length, the central mercury-containing portion is of the order of 0.2 inch in length, and the adjacent crimped portions are 0.1 inch in length, with the hermetically sealed end portions thereof being about 0.05 inch in length. Such capsules contain 6 mg. of mercury. Glass capsules of the prior art are perhaps five to six times larger than the metal capsule of the invention, and their mercury content varies from about 3 to about 8 mg. of mercury.
One immediately apparent advantage of the invention is that no tubulation is required and a panel can be baked out, filled with gas, and sealed in an oven. This simplifies the assembly operation and eliminates both the cost of the tubulation and the costs of handling the tubulation. Another advantage of the invention is that the small hole drilled in the metal mercury capsule does not permit globules of mercury to escape and enter the panel and cause problems.v Still another important advantage is that each capsule made according to the invention includes the same measured quantity of mercury.
'What is claimed is:
l. A mercury capsule comprising a tubular metal member having a central portion which contains a quantity of mercury to be released therefrom to obtain its vapor, flattened end portions of said member being bonded in intimate face-to-face contact with each other at both ends of said member to provide a hermetic seal for said capsule, and intermediate closed portions between said bonded end portions and said central portion, said intermediate portions being formed of the walls of said tubular member lightly crimped together to contain the mercury liquid in said central portion, said intermediate portions being openable under elevated mercury vapor pressure at which said hermetically sealed closed end portions are not openable whereby said capsule can be exposed to heat without being ruptured and without permitting mercury to escape. 2. A mercury capsule comprising v a metal tube of generally circular cross-section having an undeformed central portion and closed end portions closing both ends of said central portion, said central portion containing a quantity of mercury which is vaporizable and is adapted to be released from said container and into a surrounding atmosphere, said end portions each including a first portion extending from immediately adjacent to said central portion at'both ends thereof, and a second tightly closed, heremetically sealed portion extending from each of said lightly closed sections to the opposite ends of said capsule, said first portion being formed of the walls of said tube being lightly crimped together in face-to-face ,contact, and said second portion being formed of the walls of said tube being tightly and hermetically pressed together in face-to-face contact, said first portion being openable and the walls thereof being capable of being spread apart by mercury vapor at a mercury vapor pressure at which the second portion is not openable and the walls thereof cannot be spread apart.