US1318832A - Ments - Google Patents

Description

W. T. BIRDSALL.

METHOD OF EXHAUSTJNG.

APPLICATION FILED MAY 4' I915.

1 ,3 1 8 832 v Patenred Oct. 14, 1919,

WITNESSESf INVENTOR Wilfred r Biro/50H. BY

Q a9. ATTORNEY container walls.

UNITED STATES PATENT oEEIoE.

wmEEEn '1. EIEDSALL, 0E MON'I'CLAIR, NEW JERSEY, Ass IeNoE, BY MESNE ASSIGN- man, To wEsTINGH USE ELECTRIC 8: MANUFACTURING COMPANY, A CORPORA- METHOD OF EXHAUS'IING.

Specification of Letters Patent.

Patented Oct.14, 1919.

Application filed my 4, 1915. Serial No. 25,864.

To all whom it may concern:

Be it known that I, WILFRED T. BIRDSALL, a citizen of the United States, and a resident of Montclair, in the county of Essex and State of New Jersey, have invented a new and useful Improvement in Methods of Exhausting, of which the following is a specification.

My invention relates to the manufacture of vapor electric apparatus having a highlyexhausted container of vitreous material, such, for example, 'as a glass rectifier, and it has for its object to provide a simple, economical and effective method of removing deleterious gases from the interior of the container during the exhausting process. The single figure of the accompanying drawing is a side view, partially in section and partially in elevation, of a vapor arc rectifier, together with attendant apparatus necessary for carrying out my invention.

It is well known that in the manufacture of vapor rectifiers and other like apparatus requiring a high operating vacuum, extreme difliculty is encountered in removing occluded gases from the inner surfaces of the While, at the conclusion of the pumping process, the device may indicate an extremely high vacuum, yet when the rectifier is put into operation and the walls arehighly heated, it is found that occluded gases are given or which tend to lower the vacuum to such a marked degree as to seriously impair the rectifier operation. In order to remove the gases, it has been customary in the past tohighly heat the container wall during the process of ex hausting as, for example, by baking it in an oven or by assing current through the device while t e pump is still connected thereto. The oven treatment is not entirely satisfactory for, no matter how highly the oven may be heated, it is found that actual operation will set free occluded gases even though heat, ,by itself, fails to do so. On the other hand, in the ordinary rectifier, if sufiicient heat is generated by the passage of current between the electrodes to satisfactorily drive off all the occluded gases, it is found that such an amount of current is required as to seriously impair the seals.

I have found that, by surrounding a rectifier with a medium having less heat-absorbing capacity than that in which it is very high degree.

intended .to operate and by then passing current through the device, the walls maybe so highly heated as to efi'ectually remove the occluded gases and, at the same time, such a small amount of current is necessary for the required heat that the seals are not afiected.

I find that, by operating a rectifier in theair which is to be normally operated in a liquid such, for example, as water or oil, I am able to secure a vacuum of great permanence.

Referring to the accompanying drawings, a glass rectifier'bulb of conventional type is shown at 1- and embodies a pair of mam (anodes 2 and 3, a main cathode 4 and an auxiliary starting and maintaining anode 5. Connection to a pump may be made by a suitable tubulature 6. The rectifiermay be started and maintained in operation by a small are between the anode 5 and the oathode 1, current being derived from any suitable direct current source, such, for example, as a battery 7. Load current for the main anodes 2 and 3 is derived from a transformer 8 and may be adjusted in voltage by suitable taps 9 and 10, and may be adjusted in amount by a suitable rheostat 11. The rectifier 1 is designed to be operated in a cooling fluid, as, for example, by immersion in a tank 12. On account of the much higher heat absorption of a liquid than of the atmosphere, the container 1 would be, heated to collapse were it attempted to' run full-load current therethrough in the atmosphere. In the process of manufacture, however, I first exhaust the tube -1 in the ordinary manner and then pass current thereto from the source 8 in such amounts as to heat the container to a The amount of current necessary for this operation is small, owing to the low heat radiation, and I am enabled to obtain a very high heating of the container wall without using undue amounts of energy and without endangering the seals. At the same time, abnormally favorable electrostatic conditions are rovided within the container 1 for the li eration of occluded gases.

With the above described process, the gas may 'be efl'ectively removed from the container walls, but the abnormally high vapor pressure caused by the'small heat-radiating capacity produces a stringing of the are and the heating of the anodes only in small sharply defined spots. The next ste in the complete exhausting process is, in e ect, the converse of that above described. In order to heat the entire anodes thoroughly, it is necessary to provide an abnormally high vacuum and this result may be obtained by surrounding the rectifier with a medium of greater heat-absorbing capacity than that employed in normal operation. If the rectifier is designed to be submerged in the liquid of the tank 12, when, under normal load, the desired abnormal cooling may be provided by immersing a cooling coil 14 in said liquid and by circulating brine or a similar fluid therethrough. The vapor pressures within the rectifier will then be reduced to an abnormally low amount, so that substantially all the current flow within the container takes place by current carriers originating at one terminal and passing to the other so that a great share of the energy represented by the voltage drop within the device is delivered at the anodes, heating all portions thereof to a higher degree than would be the case in normal operation and effectively driving ofi' the occluded gases therefrom. After the exhausting process has been completed, the entire device may be left in the liquid of the tank 12 for normal operation and it will there, at rated load current, never be subjected to as severe treatment as that just described. The vacuum will therefore be substantially unaffected by liberation of occluded gases during normal operation.

I may provide the conducting leads to the difierent electrodes with heavy insulating coatings 1313, as shown, in order to prevent short circuiting of the device and harmful electrolytic action if an operating cooling medium of conducting material, such for example, as water, be employed.

I have described my invention as applie to the air treatment of a bulb which is to operate under water, but I desire to have it skilled in the art that it is susceptible of Various minor changes and modifications without departing from the spirit thereof, and I desire, therefore, that no limitations shall be placed thereupon except such as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. The method of liberating occluded gases from the interior of a partially exhausted vacuum; type electric device by means of heating current transmitted thereinto through the working seals thereof -which comprises surrounding said device by a less effective heat-absorbing medium than that in which it is designed to operate, passing current therethrough of substantially the same magnitude as the normal working current, and pumping out the liberated gases.

2. The method of providing abnormal gas-liberating conditions within the container of a vacuum-type electric device by means of heating current passing through the Working-current path thereof, without overloading the seals thereof, which comprises operating said device in a medium having less heat-absorbing power than that in which the device is designed to normally operate and passing substantially normal load current therethrough.

3. The method of heating a vacuum-type electric device to a gas-freeing degree by heat electrically generated therein without unduly heating the leading-in conductors thereof, which comprises immersin said device in a poorer heat-absorbin me ium than that in which it is designe to normally operate and passing substantially load current therethrough.

4. The method of removing occluded gases from the electrodes of a vapor electric device which comprises operating said device in a medium having greater heat-absorbing power than that in which it is designed to normally operate, whereby the vapor pres sure will be abnormally lowered and all ortions of the anodes will be highly heate In testimony whereof I have hereunto subscribed my name this 28th day of April,

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