US2764857A - Introducing mercury into discharge lamps - Google Patents

Description

Oct. 2, 1956 s. F. SCHAEFER INTRODUCING MERCURY INTO DISCHARGE LAMPS Filed Feb. 27, 1953 H w M w Q 0 256262 z 5652 $5352 Ell/4 57+ 5757277 l5 I9 'VOLUME m CuBn'c canrms rsrzs FROM CUMPRESSED A12 SYSTEM SYSTEM 1 FROM EXHAUST THORIUM mums:

l nvsrsv WITH INVENTOR ZE'SKH/iEI-EE j 9 IATTORVNE United States Patent INTRODUCING MERCURY INTO DISCHARGE LAlVIPS George F. Schaefer, Ramsey, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporatiou of Pennsylvania Application February 27, 1953, Serial No. 339,226

1 Claim. (Cl. 53-12) This invention relates to the introduction of mercury into discharge lamps and, more particularly, those of the high-intensity or high-pressure type having quartz envelopes.

The principal object of my invention, generally considered, is to avoid loss of part of the mercury to be introduced into the envelope of such a lamp, after the same has been accurately measured and prior to its actual reception in said envelope.

Another object of my invention is to introduce an accurate quantity of mercury into a discharge lamp, said quantity depending on the size of the lamp and the distance between electrodes, by a method involving not only facilitating the determination of the amount of mercury to be introduced, but the prevention of any loss from that amount prior to its introduction.

A further object of my invention is the accomplishing of the result above mentioned by coating the surface of the mercury droplet of measured quantity with a film of oxide of the group consisting of thoria and zirconia, said method involving one of the following alternatives:

A. The dusting with a finely powdered refractory oxide of the interior of the capsule used for introducing the droplet into the envelope.

B. Such dusting of the interior of the hollow arm or connecting tube extending from the side of the discharge lamp envelope with such an oxide, prior to pouring the mercury droplet therethrough, and

C. The application of the oxide directly to the mercury droplet prior to pouring the latter into the envelope of the discharge lamp.

Other objects and advantages of the invention will become apparent as the description proceeds.

Referring to the drawing:

Figure 1 is an elevational view of apparatus employed for estimating the capacity of the discharge lamp envelope into which mercury is to be introduced.

Figure 2 is a graph showing how the requiredweight of mercury is determined from the volume of the envelope and the distance between the electrodes, or length of the arc path.

Figure 3 is a diagrammatic view of apparatus for conveniently measuring the desired weight of mercury.

Figure 4 is a fragmentary elevational view of the left hand end portion of said apparatus, showing how mercury after being measured is introduced into a glass capsule.

Figure 5 is an axial sectional view of such a capsule, enlarged to show how it is dusted with a refractory oxide.

Figure 6 is an elevational view of a discharge lamp such as shown in Fig. 1, after the capsule has been introduced into an exhaust-preparation arm thereof, and at the time said arm is being tipped-0E after exhaustion.

Figure 7 is a view corresponding to Fig. 6, but showing the lamp and its exhaust arm at a subsequent position in which the arm and lamp have been inverted to allow the mercury droplet to fall from the capsule to the lamp prior to tipping-off its exhaust-preparation arm.

Figure 8 is a transverse sectional view on the line VIII-VIII of Fig. 6, but to an enlarged scale.

Figure 9 is a view corresponding to Figure 8 but illustrating a modification.

Figure 10 is a view showing apparatus for practicing my invention, in accordance with another embodiment.

The present method of introducing mercury into. discharge lamps, and specifically quartz lamps of the highpressure type, involves considerable difficulty at times to insure that the full amount, as that in the glass tube or capsule customarily employed in the introduction, gets into the lamp. In humid weather, or in case the glass exhaust-preparation arm which projects from the lamp envelope is not absolutely clean, the mercury droplet when introduced, as from the capsule, into said arm, on its way to the lamp envelope, has a tendency to separate into minute droplets or wetthe arm. The result is that in such an instance the correct amount of mercury does not enter the envelope of the lamp, resulting in many cases in low operating voltage so that the lamp must be scrapped.

My invention involves an improved method for correcting the above conditions. It essentially includes dusting or rolling the measured amount of mercury for each lamp in finely pulverized thorium oxide, zirconium oxide, or other similar inert or stable metal oxide. I have found that mercury when so dusted or superficially coated will roll freely and, even if it separates into smaller parts, none of it will wet the glass exhaust-preparation arm. Thus all of the measured quantity of mercury will enter the lamp. My method also considerably reduces the time required to get the mercury into the lamp.

Referring to the drawing in detail, like parts being designated by like reference characters, there is shown in Figure 1 as one embodiment, a quartz envelope 11 of a high-intensity mercury vapor lamp. Such a lamp may be of the type described and claimed in the Unglert et a1. application, Ser. No. 113,444, filed Aug. 31, 1949, now

Patent Number 2,675,496, and owned by the assignee of the present application. As such it includes main electrodes 12 and 13 and an auxiliary electrode 14 sealed into the ends thereof. This figure also illustrates apparatus for determining the volume of the envelope 11, in order to estimate the proper amount of mercury to be inserted thereinto. This amount depends, not only on the volume, but also on the arc length or distance between in a head 17, such as is conventionally used on exhaust machines, only diagrammatically illustrated. See the head 19 of the Campbell Patent No. 2,533,712, dated Dec. 12, 1950, the hand lever 25 of which corresponds with the operating lever 20 of the present case. The head 17 is connected to an exhaust system through tubing 18, said tubing having valves 19 and 21 therein and between which is connected'a glass bulb 22. The tubing 18 branches to a manometer 23 containing a mercury column 24. Adjacent one arm of the manometer 23 1s-a scale 25, calibrated in cubic centimeters to show the volume of the envelope 11.

The arrangement disclosed is used by first exhaustingwith'the valve 19 closed and the valve 21opened. The valve 21 is then closed and the valve 19 opened. This employs the vacuum produced in the bulb 22 to draw some of the air from the envelope 11 and create a partial vacuum in the system, represented by a rise in the left hand column of mercury 24 to the position illustrated, whereby the calibrated scale 25 shows the volume of said envelope, in this instance 17 cc.

This reading, of 1-7 is employed by using the chart shown in Fig. 2 to determine the required weight of mercury in milligrams. The arc length in millimeters enters the picture, as shown in this figure, as each line of the graph is drawn in accordance with an arc length, that is, are lengths from 57 mm. to 63 mm. are shown. So the required weight of mercury is determined by running from the point of intersection of the ordinate marked 17', representing the volume, and the graph 57, representing the arc length, horizontally to the scale of "mercury weight, where the reading. of 86 is found, meaning that 86 mg. of mercury are required for such an envelope.

While this amount of mercury may be weighed out on a chemical balance and used, as will be understood, yet my preferred method of measuring is to draw the mercury into a capillary tube 26, as shown in Figure 3, the Weight of the mercury being determined by its length in the capillary from the inlet or left hand end, as shown by the scale 27'.

The mercury is drawn from a receptacle 28 containing a supply 29 thereof, by means of a connection through a valve 31 to an exhaust system, as indicated. This drawing into the capillary to the proper length is controlled by carefully opening the valve 31, while the system is otherwise closed by the operators finger 35 and the valve 3'8, to draw up the mercury column 32. If the column is' drawn up too far, it may be released or allowed to fall back by closing the valve 31 and carefully admitting some air to the rubber tube 33, connected to the extension 34 of the tube 26, by allowing leakage past the operators finger 35.

When the desired amount has been measured, the receptacle 28 is withdrawn, the capsule 36 (Fig. 4) into which" the mercury is to be placed is positioned under the pointed end 37' of the tube 26, and the measured quantity of mercury discharged thereinto by, with the valve 3-]: and finger 35 closing the system, the latter serving to adjust the pressure, carefully opening the valve 38 from a compressed air system.

In accordance with my invention, the capsule 36 prior to reception of'the mercury droplet 38, is coated on its interior, as by dusting, with an inert metal oxide, such as 'thoria, zirconia, or some other refractory oxide powder, either harmless or beneficial to the lamp during operation. This dusting may be effected by placing a quantity of such capsules in a jar (not shown) pouring a quantity of thoria into said jar, and stirring, rolling or otherwise agitating the mass until the thoria, or other selected oxide, has worked into the interiors of said capsules. The capsules are then removed, one by one, and their ex teriorswiped oil, whereupon they are ready for the reception of mercury droplets 38'.

Mercury from said capsules is introduced, preferably into an. exhaust-preparation arm 39 (Fig. 6) extending from an envelope 1]., as by being sealed to the tube 16 extendingztherefrom at a point indicated at 41. This exhaust-preparation arm 39 comprises a quartz portion 42', sealed directly to the quartz tube 16, and a graded-seal portion 43, terminating in a glass portion 44, which may be of the type designated by the trade-name Nonex, although any glass, which is readily scalable to the part 43 and thereafter tipped-off, may be employed.

The capsule 36 containing the droplet of mercury 38 is pushed up into the tubular portion 44, to the position approximately illustrated in Fig. 6, toward the envelope 11 asv the exhaust-preparation arm 39 is depending therefrom. The capsule 36-may be held in this position by means of an inverted V-shaped spring 45 with its diverging ends engaging the inner wall of the tube 44 and the capsule resting on the apex of this inverted V-shaped spring. The tube portion 44 is then inserted in an exhaust head 46, corresponding generally with the head 17, through which the arm and connected tube 11 are exhausted in a conventional manner, as will be understoodi- After the tube 11 is exhausted to the desired degree, the tube 44 is tipped-elf, as indicated at 47, as by meansof apointed gas flame 4S issuing from a burner 49.

The envelope 1 audits connected exhaust preparation arm are then inverted to the position represented in Figure 7. This allows the capsule 36 to drop by its weight from the apex of the V-shaped spring 45 to the position illustrated, where it encounters a restricted portion 51 in the tube 44 thereby stopping it from further movement while the now reversed \l-shaped spring 45 remains fixed by itsv tension in the tube 44, as shown in Fig. 7. The

mercury droplet, however, the surface of which has been coated with powder from the inner surface of the capsule 36, passes directly through the portions 43 and 42 into the envelope 11, and is represented at 38. The tubular portion 42 is then tipped-off, as at 52 by the sharp flame 53, and the lamp of the envelope 11 is then ready for use.

Figure 9 represents a modification in which the tubular portion 44 of an exhaust-preparation arm is coated interiorly with a finely powdered refractory oxide, such as thorium oxide or zirconium oxide, as indicated at 40, so that the mercury droplet being introduced becomes coated by contact with said portion 44*. This is an alternative to the coating of the capsule 36 of Fig. 5, as indicated at 40". But it will be understood that, inasmuch as the exhaust-preparation arm may be used over and over again, it will gradually become coated with such oxide if capsules 36 are so coated and used therewith, so that' after such use it may not then be necessary to coat such capsules 36.

Figure 10 represents another embodiment in which the mercury'droplet 38 is coated or dusted with powdered thoria or zirconia 40*, by being placed in a glass disk 54, alongside a quantity of the selected oxide, and mov ing it around in' contact therewith until its surface is coated with said oxide. The droplet 38 may then be employed for insertion into an envelope 11, as by dropping it directly into an exhaust-preparation tube thereof, or by placing it in a capsule 36 and employing it in the manner heretofore described.

Although preferred embodiments have been disclosed, it will be understood that modifications may be made within the spirit and scope of the invention.

I claim:

The method of introducing an accurate quantity of mercury into a discharge lamp comprising dusting the interior surface of a small glas capsule with a powdered oxide of. the group consisting of thoria and zirconia, measuring the desired quantity as a droplet of mercury, placing said droplet in said dusted capsule, introducing said capsule into a tubular arm attached to the envelope of said lamp, exhausting said envelope through said arm, tipping off said arm beyond said capsule from said envelope, inverting to allow said mercury to flow from said capsule to said envelope, and tipping-oil said arm from said envelope.

References Cited in the file of this patent UNITED STATES PATENTS

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