US1346408A - High-vacuum pumping system - Google Patents

Description

W. V. LOVELL.

HIGH VACUUM PUMPING SYSTEM.

APPLICATION FILED MAY 26. 1917.

1,346,408.y Patented July 13,1920.

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u wlan-m Il): n all) lTll il l nimm-lul nlnll In UNITED STATES WILLIAM V. LO'VELL, 0F ,WILKINSBURQ HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION F PENNSYL- Vania.

FICE.

PENNSYLV ANIA., ASSIGNOR 'IO WESTIG- HIGHVACUUM P UMPING sYsTEiv'i.

iaatos.

To all whom il may concern:

Be it known that I, WILLIAM V. LovELL,`

Y a citizen of the United States, and a resivented a new and useful Improvement in High-Vacuum Pumping Systems, of whichV the following is a specification.

My invention relates to pumping systems particularly adaptedfor the production of high vacua, and it has for its object to provide a system of the character designated that shall be compact in construction and efficient, inexpensive and effective in operation. i

More specifically, my invention relates to that class of apparatus known as vapor or diffusion pumps, and it has for its object to provide apparatus whereby the condensate!v from the diffusion pump may be employed in a Sprengel pump or fall-tube to produce the preliminary or roughing vacuum.

The single figure of the accompanying drawing is a side view, partially in section i and partially in elevation, of al pumping system embodying a preferred form of my invention.

In the production of extremely high vacua, such, for example, as are employed in vapor converters for the rectification of alternating current, the apparatus known as the diffusion pump has recently attained considerable prominence. Such apparatus has been disclosed and discussed in a' number of' technical articles, as, for example, in apaper entitled A high vacuum mercury vapor pump of extreme speed presented by Langmuir before the American Physical Society in April 1916,4said paper being noted on page 49 of the Physical Review for July 19 16. In its essence, said apparat-us comprises means for producing a blast of substantially pure vapor such, for example. as mercury. said blast being delivered in such relation to the mouth of the exhaust tube that the gas in the conhaving its pressure radically increased.

what in dispute but. apparently, there is some mechanical entraining. the apparatus working as does the ordinary injector and, xpparently. there is also a tendency for the cas foibe pumped to diffuse through the tainer is entrained thereby and swept away,

The exact method of operation is still some-- Specification of Letterslatent. Patented July 13, 192() Application led May 26, 1917. Serial No. 171,218. i I

material of the' vapor blast, thus giving rise to the -term diffusion pump.

The apparatus thus described is well adapted for raising t-he pressure of a gas from the extremely low pressures desired in Vvapor converters to the pressures which are vattainable by ordinary mechanical pumps but it is incapable of pumping toatmosplieric pressure and it must, therefore, be operated in tandem.witli an ordinary mechanical pump which receives the gas .at the final p ressurcof the diffusion pumpand .raises it to atmospheric pressure. Back? ing or roughing pumps of this type are expensive and entail additional care and trouble in their maintenance. v.By my invention, I may do away entirely 1th the necessity for using a distinctly operating roughing pump, diverting the condensate from the diffusion pump into a fall-tube and there causing it to act upon the relatively high-pressure gas givenofi by the diffusion pump,` raising said gas to atmospheric pressure and permitting its escape, or I may employ a simpler and cheaper roughing pump usual system.

Thus, it will be noted thatAI employ a .pumping substance such, forv example, as mercury, in two vdistinct stages.v In the first place, said substance is used in the formbf vapor to produce an initialy com- 'pression and is then used in the form of liquid to producestill further compression.

Referring to the drawing for a more dematerial 6 so as to maintain a relativelyV y high temperature in the vincoming vapor' blast, and the upper portion of the cham- `berl is preferably provided with a cooling jacket 7 to condense lthe vapor blast when it reaches the upper portion of said chamber. The Acontainer 8 to be exhausted is connected to the pump 1 by a tube 9, said tube discharging into the chamber 5 adjacent to the mouth of the nozzle 4:. A tube `1i() vprojects from the upper portion of the chamber 5 and extends downwardly a sulficient distance to produce `a barometric vacuthanA is demanded by the pool of liquid 11. The upper end of the a continuous' circulation nozzle 4: is some distance above the floor of the chamber 5 and the condensate from the upper portion of said chamber is thereby collected to forma pool 12. The level of the upper surface of the pool 12 is determined by a drainage tube 13 that discharges into the fall-tube 10. A return tube 14, which may be closed by a valve 15, connects the pool 11 to the boiler 2, thus permitting of the pumping medium.

Having thus described the structure of` a pumping system embodying my invention, the operation thereof is as follows. The valve 15 is closed to retain liquid in the boiler 2; Said liquid is brought to the boiling point by the heating means 3 to cause a blast of vapor to issue from the nozzle f1 p and sweep by the mouth of the tube 9. Gas,

drawn from the container 8, is mechanically entrained thereby and diffused therethrough and is swept to the upper portion of t ie chamber 5. At this point, the vapor issuing from the nozzle 4 is condensed and drips back into the pool 12, leaving the entra-ined gas free to pass into the tube 10. The result of this action is to produce a somewhat higher gas pressure in the upper portion of the chamber 5 and in the tube 10 than exists in the container 8 and in the tube 9. The continued condensation of the vapor blast causes the overflow of the pool 12 into the tube 413 whereby successive globules of liquid descend in the tube l0, carrying with them compressed gas drawn from the upper portion of the container 5, as in the ordinary Sprengel pump. The gas is released in the pool 11 and escapes to the atmosphere and, as soon as a partial vacuum is formed, the Valve'15 may be opened to permit the condensate to be ,sucked up through the tube 1.4 toaagain participate in the pumpingcycle.

he system which I have described to this point is operative Hto produce extremely high degrees of vacuum but is rather slow in its action, as the Sprengel pump is necessarily of low capacity, if3 operated by the condensate from the'diffusion pump. It is sometimes' advisable, therefore, where rapid pumping is required, to employ a mechanical pump, as shown `at 16, said pump being connected to the fall-tube 10 through a valve 17. In operation, the roughing pump 16 may beV operated to produce a partial vacuum in the chamber 5, rapidly producing the degree of vacuum where the Sprengel and diffusion pumps may come into action most effectually, the pump 16, however, being far simpler and cheaper than would be permissible if said pump were operated directly in tandem with the diffusion'pump alone.

1. The combination with a diffusionv pump, of a Sprengel pump in series therewith and means whereby the latter is operated by the condensate of said diffusion Pump'- 2. The combination with a mercury diffusion pump, of'a Sprengel roughing-pump in series therewith, and means whereby said roughing pump is operated by the mercury condensed in said diffusion pump.

3. In a pump, the combination with a fluid boiler, of a closed container provided with heat-dissipating means, a nozzle connected to said boiler and arranged to pro- `ject a vapor blast into saidcontainer, an inlet port in the wall of said container adjacent to said nozzle, -an outlet port in the wall of said container opposite said nozzle, a fall tubel connected to said outlet port and terminating beneath the surface of a liquid pool, and a drainage tube from the lower portion of said container to said fall-tube, whereby gas, entering at said inlet port, is entrained and diffused in said vapor blast, swept onward and compressed thereby at said outlet port and withdrawn therethrough by the action of condensate enter-y tube through said drainage densate pool of said diffusion pump to said fall-tube, said fall-tube terminating beneath thesurface of a liquid pool, and a return tube from said pool to said boiler, whereby the material of said pool is caused to circulate through said boiler, the vapor blast, and

said fall-tube.-

6. The method of employing a substance l in pumping a highly raried gas which comprises vaporizing said substance, compressing said gas by a blast of said vapor, condensing said vapor, and further compressing said gas by the fall of the resultant condensate.

7. The method of employing a substance in the compression of a gas which comprises rst acting upon said gas by a Vapor blast of said substance to produce initial compression thereof, converting said substance into liquid form and then further acting upon said gas therewith.

8. A pumping device for raising the pressure of a gas which comprises a body of v liquid, means `for vaporizing said liquid,

means for producing a blast of the resultant vapor in such relation to said gas as to continuously entrain and compress the same, means for condensing said vapor, and means whereby the resultant condensate is caused to move so as to again entrain and still Ifurther compress said gas.

9. A pumping system comprising a diffusion pump, a Sprengel pump, and a inechanical pump connected between said other two pumps', and means whereby said Sprengel pump is operated by the condensate from said diffusion pump.

ln testimony whereof, I have hereunto subscribed my name this 11th day of May, 1917.

TVlLLIAM V. LOVELL.

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