US1028636A - Method of exhausting vessels. - Google Patents

Description

U l STTES CHARLES J. THATCHER, 0F UPPER NYACK, NEW YORK.

METHOD OF EXHAUSTING VESSELS.

No Drawing.

To all whom it may concern Be it known that I, CHARLES J. THATCIIER, a citizen of the United States, and a resident of Upper Nyack, in the county of Rockland and State of New York, have invented a certain new and useful Method of Exhausting Vessels, of which the following is a specification.

The process which constitutes this invention relates to the exhaustion of any vessels whatsoever in which it is desirable to rapidly and economically attain high vacua. It may be used either for exhausting electrical apparatus which are permanently provided with electrical conductors or terminals, such as incandescent lamps, vacuum tubes, etc, or for exhausting nonelectrical apparatus provided with suitable conductors or terminals only for the purpose of exhaustion.

The object of this invention is therefore to attain high vacua in any vessel requiring completeexhaustion, and the invention consists in effecting this in a rapid and economical manner without introducing into the vessel, or otherwise employing, any gas ab sorbing substance.

It is well known that complete exhaustion of vessels to high vacua by mechanical pumping alone is a slow and somewhat costly procedure. The difficulty lies in the exhaustion of the last traces of gas.

My invention relates more particularly to the rapid removal of these last traces of residual gases remaining after mechanical exhaust-ion.

At the present time, so far as I am aware,

the only process of rapid exhaustion is that used in the manufacture of incandescent lamps and set forth in U. S. Patent #537,693 to Arturo Malignani. Three steps are essential to the operation of this process. They are the preliminary mechanical exhaustion of the lamp to a pressure of about 2 mm. of mercury; the intensive incandescence of the filament of the lamp in this attenuated atmosphere and at a sufficient intensity to produce a characteristic faint bluish haze throughout the interior of the bulb; and lastly, the vaporization of a suitable solid substance, such as arsenic, iodin, sulfur, phosphorus, etc., previously deposit ed in some convenient locality Within the interior of the lamp bulb. The process of said patent also comprises additional elespecification of Letters Patent.

Application filed March 30, 1910. Serial No. 552,310.

Patented J une 4, 1912.

to the three fundamentally essential elements above referred to. These tributary steps have been modified in Letters Patent, and in commercial practice to some degree, as regards the means employed for carrying them out and the sequence of their performance. Otherwise the modern practice of incandescent lamp exhaustion is substantially identical with that devised by Arturo Malignani in 1894 and disclosed in his Letters Patent. In all of these modified procedures as well as in the Malignani process itself, the extraneous solid substance deposited within the lamp combines with and precipitates, when it is vaporized, practically all of the gases in the lamp interior, accompanied by the disappearance of the blue haze.

My process, as applied to incandescent lamps, differs from that just considered in that I secure a high vacuum without the use of any such extraneous solid substance. I extend the preliminary mechanical pumping so that a vacuum is obtained which is generally higher than that proscribed by Malignani or than that attalncd by mechanical pumping in the practice of his process. I then institute the intensive incandescence, proper, of the filament, whereupon a decrease of pressure which is equal in extent and rapidity to that produced by the Ma lignani process at once occurs.

.The exhaustion of lamps from 2 mm. down to say 0.2 mm. is therefore effected by my process merely by the continuation of mechanical pumping instead of by the use of vapors of solid substances as by Malignani. The completion of exhaustion, i. e. from 0.9. mm. down is effected by the same means in both processes, namely by the intensive incandescence of the filament for the same length of time and with the same result, as has been shown by investigation. ()perating in this manner, the use of suitable substances as disclosed by Malignani may be entirely dispensed with and an equally high vacuum is obtained in substantially the same time-or even less as I will later show. Since this method of procedure does not vary in any manner the degree or duration of the intensive incandescence'of the filament as now employed in the exhaustion of incandescent lamps, it is obvious that the filaments will not undergo any changes which do not occur in the process of exments or steps which I consider tributary haustion now universally employed, and that they are therefor not injured by the practice of my process.

It has been demonstrated that filaments which are ordinarily used in incandescent lamps have initially a certain ability to precipit-ate gases in comparatively high vacuum, but lose this ability after they have been incandesced for a period, particularly at voltages above those they are designed for. The ability of these filaments to .precipitate the gases in comparatively high vacua is limited, moreover, asto the amountof gas which they are able to remove. There exists, in other words, a certain proportionality between the size of a filament and the amount of gas which it will precipitate; at all events, this is borne .out by the fact that a rapid reduction of pressure to very high vacua occurs with certain small and limited quantities of gas at certain low pressures, but does not with larger quantities at higher pressures. In view of these considerations it is apparent that the practice of this process in vessels" containing solid conductors requires the use of a con-- ductor or filament which has not previously been lighted for any appreciable time, particularly at intensive incandescence, and requiresalso a suitably extended preliminary mechanical exhaustion of the vessels. It was the realization of the necessity of these conditions and the practical application thereof to the exhaustion of vessels without the use of extraneous suitable substances which enable me to devise the herein described process. This limited precipitating power of electrical conductors may be termed their normal, intrinsic precipitating power, for it represents that normal quantity of gas which can be rapidly removed from a rarefied atmosphere Without any pronounced or recognizable disruptive effects on the eon-' ductor itself, and-- whichremoval is cocasloned by phenomena Which are lntrmsic to an electrical conductor during the passage of a current. This normal, intrinsic precipltatlng power can be readily ascertained by a few appropriate trials with any size of the walls of the vessel.

suitably arranged apparatus. By decreasing, step by step, the pressure in the apparatus before the current is first passed through the conductor in each trial, a certain pressure will finally be reached in which a decrease of pressure down toa very high.

vacuum occurs with great rapidity. The normal, intrinsic precipitating power will always vary, naturally, with the size and nature of the conductor, the intensity of the current passed therethrough, and, apparently, with the nature, condition and In view of these many factors, it is impossible to specify the maximum quantity or pressure of gas which can be exhausted from any certain piece of apparatus, but by means of the directions above set out, any one skilled in procedures of this nature will readily ascertain the normal, intrinsic precipitating power of a conductor during the passage of a current of a suitable high intensity.

In lamps containing carbon filaments it has bee-.1 customary to attach the filament to the leading-in wires'by means of what.

are technically known as clamps. These latter are composed usually of a paste composition containing carbonaceous materials which decompose when the filaments or clamps become red hot, and evolve gas in considerable quantities thereby. For this reason the carbon filaments of the lamp have to be worked as it is termed, either during the final stages of mechanical exhaustion or immediately thereafter. A very high vacuum cannot be attained or maintained in any incandescent lamp containing such or simi-- lar clamps untll these gases have been evolved.

In carrying out the herein described process which constitutes my invention, with vessels containing solid conductors and clamps of this character, it is obviously necessary,in

order not to destroy the normal, intrinsic precipitating power of the filament, to effect the working of the clamps without any considerably extended incandescenee of the filament. I may employ any means to effect this result, but have found in practice that the carbon filament of an incandescent lamp is still able to precipitate gases at a pressure of 0.2 mm., more or less, provided the working of the clamp has been carefully and rapidly executed. That is, the filament is not injured for. the practice of my process providing the clamps are worked by first turning on the current after the pressure has been reduced to about one millimeter, or preferably less, by mechanical pumping, and while the same 'is continuing then increasing the current rapidly to the minimum intensity which will cause the clamps to become red hot in a few seconds. I maintain the filament and clamps at this degree of incandescence for a few seconds longer and then immediately shutoff the'current and continue. the pumping down to the necessary low pressure corresponding to the normal, intrinsic precipitating power of the conductor. In carrying out this workmg, I must emphasize, it is advantageous to initiate it at a tolerably low pressure, something less than one millimeter, for the clamps then more readily acquire and retain a red heat.

After practically all the gases contained in the filament and clamps have been thus evolved, and thelamp has again been brought down to a suitablelow vacuum by continued pumping, I institute the intensive which would obviate the necessity of such' a procedure may be employed in combination with my method of removing gases at low pressures. In lamps containing filaments and clamps of any description which would not evolveg as'es in any detrimental amount upon the initial incandescence of the filament this working in the above described manner, or in any other, may be, of course,

dispensed with. In a somewhat analogous manner, traces of residual gases may be removed from vessels by passing a suitable current through the gases themselves by means of terminals. The current must be sufficiently intense to overcome the resistance of the vacuous space, and to suitably ionize it and produce a pronounced luminous discharge in the vessel practically until the desired final gaseous pressure is obtained. In this modification, also, the amount or mass of residual gas within the lamp should not exceed the normal, intrin-:

sic precipitating power of the electrically excited conductor, which value may be ascertained for any type of vessel by a few appropriate trials as before explained.

A treatment similar to the working before referred to may be carried out in vessels containing gaseous conductors, provided it is rendered necessary by the presence of substances, on or near the terminals or in other interior portions of the vessel, which might evolve gases either during the process of exhaustion or in actual use. Any vessel, indeed, exhausted by my process,

should be previously heated by some suit able means sufficiently to drive off from the interior walls the films of water or gas which normally adhere to the surfaces of solids. After either or both of these treatments have been efiected and the gas or vapor thus evolved has been pumped out until a suitable pressure corresponding to the normal, intrinsic precipitating power of the conductor has been reached, the process of exhaustion is completed by passing a current of suitable intensity through the vessel as before explained, and preferably after the pump has been shut ofi My process can of course be carried out by other means and in other Ways than those specifically described. For example, the exhaustion of incandescent lamps can be effected bythe passage of a suitable current, not through the filament of the lamp itself but through a supplementary solid. conductor or even through the residual gases of the lamp, after the filament has been worked as before explained if necessary, and after the lamp has been exhaustedby pumping or other means to a pressure corresponding to the normal, intrinsic precipitating power of the conductor used for this purpose. TlllS procedure would bepreferable in lamps containing very sensitive filaments, which would be damaged by even a brief period of intensive incandescence, and in low voltage lamps. My process may, indeed, be thus carried out with lamps of any description whatsoever, in which it is thought that the filament is unsuitable, or might" be injured by reliance upon it, to eflect exhaustion as herein set forth. Such aprocedure entirely dispenses with even the period of intensive incandescence of the filament now employed in the exhaustion of incandescent lamps and obviates any damaging effects to the filament arising therefrom. One method of safeguarding the filament in this way would be to eifect the exhaustion by the passage of a current through the gases of the lamp by means of suitably applied external terminals or auxiliary internal terminals.

It will of course be understood that I do not confine myself to the specifically described methods of passing electrical currents through exhausted vessels or suitably ionizing or electrically exciting the gases in their interior.

By exhausting vessels according to the herein described process certain practical and important advantages result. Thus it -is economical to dispense with the use of a suitable gas-absorbing substance in exhausting incandescent lamps. Although the process of exhaustion now employed requires the use of a very small amount of a suitable substance such as phosphorus, the total cost of the same and of its deposition in'the tubultures of large numbe'fs of lamps is considerable. By my process the tubulture can be made shorter. The consequent saving in glass tubing amounts to a further considerable item.

Incandescent lamp exhaustion by my process is also more economical than the present practice in that it requires less attention on the part of the lamp operator and is, In reality, more rapid. A comparatlvely large number of lamps can be attached to each pump and the mechanical exhaustion can then proceed while the operator is attaching or attending to another S8I'1E.S 0f lamps. After the properyacuum hasbee'n reached, as ascertained if desirable by a readlng of the gaseous pressure by means of a suitable gage attached to each series of lamps, the current can then be'turned on 1n all of the lamps simultaneously and continued until the exhaustion is completed. A determination of the pressure common to all the lamps can now be made again and in a very few seconds by the said gage, to insure that the requisite high vacuum has been attained; or the disappearance of the blue haze may be relied upon todetermine this point. By a suitable arrangement of gas jets the lamps maythen be all sealed of]? simultaneously and the current finally turned 011'. With a fairly good pump, a vacuum of 0.2 mm. or less can be attained in considerably less than 2 minutes as contrasted with the 30 to 60 seconds of mechanical exhaustion now employed in the operation of the Malignani process. But even allowing as much as 5 minutes for mechanical exhaustion, during which time the operators attention can be given to another series of lamps, the exhaustion of a bank of twenty orlmore lamps by my process will not occupy ten minutes altoget-her, or less than -1- minute per lamp.

This method of'procedure, rapidity of cx-.

haustion and output per operator cannot be duplicated, by the present practice of lamp exhaustion, as each lamp requires individualattention and treatment on the part of the operator during the critical portion of the exhaustion. In addition to these advantages the hereindescribed process is superior to that now in use in that it more per: fectly insures the continuance of a high vacuum in the lamp during actual use. The

gases are precipitated by my process in a more stable and permanent combination than by the present practice. The substance, phosphorus, which is now used, and which hold the gas in physical combination as I have demonstrated, is vaporized in the lamp bulb at comparatively low temperatures. The temperature which will produce this eflect is easily reached during actual use of the lamp, and upon vaporization of the phosphorus it liberatessome or all of the gas with which it is combined. The condltlons under which the combination of the residual gases with phosphorus originally occurred are not duplicated in actual use. This liberation of gas and impairment of the vacuum, when once started, is cumulative and results in a considerable reductlon in the useful life of the lamp. This effect cannot occur when my process is used, for the gases are precipitated and pennanently held in combination with practically non-vaporizing particles such as carbon, tungsten or the like.

I claim 1. The process of rapidly producing high precipitate the residual vacua in vessels, which consists in subjecting them to a suitable preliminary mechanivacua in'ineandescent lamps, which consistsin subjecting them to a suitable preliminary mechanical exhaustion and passing a sultable electric current through the lamps to 3 gases and complete the exhaustion. 3. The process of rapidly producing high vacuain incandescent lamps, which consists in subjecting them to a suitable preliminary mechanical exhaustion, and then bringing the filaments to intensive incandescence to complete the exhaustion.

4. The process of rapidly producing high vacua in incandescent lamps, which consists in subjecting them to a suitable preliminary mechanical exhaustion and then bringing the-filaments to intensive incandcscence to precipitate the residual gases andcomplete the exhaustion.

5. The process of rapidly producing high "acua in'vessels containing an electrical conductor, which consists in mechanically exhausting them until the mass of gas within the vessels does not exceed the normal, intrinsic,precipitatingpower of the conductor, and then passing a suitab e electric current through the conductor to precipitate the residual gases and complete the exhaustion.

6. The process of rapidly pr ducing high vacua in incandescent lamps, which consists in mechanically exhausting them until the mass of gas within the lamps doesnot exceed the normal intrinsic, precipitating power of the filaments, and then bringing the filaments to intensive incandescence to complete the exhaustion.

'7. The process of rapidly producing high vacua in incandescent la1nps,which consists in mechanically exhausting the same to a pressure not exceeding two-tenths of a millimeter of mercury, and then bringing the filaments to intensive incandescence to com-.

plete the exhaustion.

Signed at New York, in the county. of

CHARLES J. THATCHER.

Witnesses:

LAURA E. SMITH, FREDK. F. SCHUETZ.