US2591334A - Vacuum pumping apparatus - Google Patents

Description

April 1, 1952 J. H. BLACK ET AL VACUUM PUMPING APPARATUS Filed Sept. 1, 1950 BY 91h JUDD H. BLACK HORACE G. WARREN INVENTORS ATTORNE rs Patented Apr. 1, 1952 VACUUM PUMPING APPARATUS Judd H. Black and Horace G. Warren, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application September 1,1950, Serial No. 182,862

This invention relates to apparatus for producin vacuum and is particularly concerned with vacuum pumps of the type wherein organic pump fluid vapors are passed through paired ejector and difiuser elements and condensed.

It is an object of this invention to provide improved apparatus for producing vacuum.

It is a further object of this invention to provide improved ejector pumps of the type employing organic pump fluid vapors for evacuation in the high vacuum range.

Another object of the invention is to provide a high vacuum pump of the ejector type having a more compact structure than obtainable when spent pumpiiuid is returned to the pump boiler by gravity flow alone.

Another object of the invention is to provide a high vacuum pump of the ejector type having no movable parts ordinarily subject to mechanical failure.

Another object of the invention is to provide acting means for returning condensed organic pump fluid to the boiler against pressure in the boiler.

Another object of the invention is to provide a high vacuum pump of the ejector type including means for returning condensed pump fluid from the paired ejector-diiiuser elements to the boiler of the pump against pressure in the boiler,

which means is responsive to changes in the pressure in said boiler.

Another object of the invention is to provide means for positively impelling condensate from the ejector-diffuser assembly to the boiler of a high vacuum pump without increasing the power consumption of the pump to an objectionable degree.

Another object of the invention is to provide ahigh vacuum ejector pump of the type employing organic pump fluid and including means for "utilizing a portion of the pump fluid vapors to return condensed pump fluid from the pumping zone of the pump to the boiler against boiler 3 Claims. (01. 230--101) a high vacuum ejector pump including positively ferred form.

Vacuum pumping apparatus embodying this invention is of the type wherein vapors of organic pump fluid produced in a, suitable boilerare passed through paired ejector and difl'user elements, condensed and returned to the boiler, the pump fluid vapors exerting a pumping action by passage through the paired ejector and difiuser elements whereby a system connected to the pumpin apparatus is evacuated.

In the preferred embodiment of the invention as illustrated in the drawing, the vacuum pumping apparatus comprises pumping means adapted to be connected to the system to be evacuated, vapor-generating means connected to the pumping means for delivering vaporized pump fluid to said pumping means, and condensate return means connecting said pumping means with said vapor-generating means.

The pumping means of the preferred apparatus comprises a diiiuser element It! and an ejector element H arranged in pumping relation with the nozzle of ejectorelement H directed into the throat of diffuser element ID. A condenser coil I 2 connected to a source'of COOIiIlg' fluid (not shown) is positioned around the diffuser element It] in heat conducting relation therewith, coil I2 extending around at least the portion of diffuser element In remote from ejector element H and preferably around element I 0 substantiall throughout the length of element 10.

The vapor-generating means comprises a boiler l3 spaced below the pumping means and adapted to contain a body of organic pump fluid, such as a phalate ester or sebacate ester or the like, and including a suitable heater element 14. such as an electrical immersion heater or other conventional heating means. Boiler I3 is connected to ejector element I l of the pumping means by primary vapor conduit l6, conduit l6 being of the lower end of diffuser tube l'lwith boiler 13,

a jet nozzle 2| directed downwardly into the throat of diii'user tube and a secondary vapor conduit 22 connecting jet nozzle 2| with primary vapor conduit It at a point alon primary vapor conduit IB between boiler is and ejector element H.

In the preferred embodiment, diffuser element H! in accordance with conventional construction practices is flared at the low pressure end of the element l adjacent ejector element H and is convergent fromthe low pressure end toward a constricted throat and thence divergent at the high pressure or exhaust end of diffuser element Ill. Diffuser element It includes an inlet port 23 at the low pressure end of the diffuser element It, which port 23 is adaptedto be connected to the system to be evacuated. An outlet or exhaust port 24 at the high pressure end of diffuser element It! isarranged for connection loat a point-behind the mouth of ejector element H: whereby backstreaming of pump fluid vapors into thespacebeing evacuated is minimized.

Referring to the condensate return means,

diffuser tube I! comprises a downwardly convergent upper portion, a constricted throat and a downwardly divergent lower portion. Jet nozzle 2|, which is preferably flared outwardly to-the jet mouth, is directed downwardly into I theconvergent upper portionof diffuser tube 9'! towards the constricted throat of difiuser tube 1?. Condensate. conduit I8 connecting diffuser ele- 'ment, 1 i! and diffuser tube ll opens into the upper end-10f diffuser tube I! at a point not lower than the mouthofjet nozzlell. embodiment wherein diffuser element It] is generally horizontally disposedandcooled by con- .denser coil I21 substantially throughout its length, condensate. conduit I8 is branched and connected In the preferred to both ends of diffuser element Ill. Secondary eondensateconduit [9 connecting the lower end of-diffuser-tube H with boiler l3 desirably opens into boiler 43- below the normal level of pump 7 fluid-in the boiler I3.

' The secondary vapor conduit 22 connecting jet nozzle 2|- with; the primary vapor conduit i6 is desirably of substantially smaller diameter than the primaryvapor conduit [6. In order to condraining pump fluid from the boiler. If desired,

. amanometer 21 can be connected to the boiler l3 ment It and expand into the divergent high pres sure end of difluser element l0 thereby evacuating the system connected to inlet port 23.

During passage through diffuser element iii,

' condensate is impelled by the pump fluid vapors serve heat, boiler [3, primary vapor conduit i3 7 and secondary vapor conduit 22 are lagged throughout their extent as indicated at 28, 28. Drain cap 25' on boiler 13 provides means for and diffuser element it for measurin the boiler p-p essura circulated through the condenser coil. I2. A suitable o a i ump fluid s c -a phalate te sebacate ester, tetrasilane or other well-.lrnown pump fluid is progressively vaporized in boiler 13 by means of heater element M. Pump fluid vapors generated in the boiler are channeled upwardly through primary vapor conduit Hi to ejector-element II. The vapors are. ejected h .uehthe mouthoi e ec l m n p 1 are an th cons r cted j hroa or; d fl s r l which are conducted from the primary vapor conduit it to jet nozzle 2! by secondary vapor conduit 22, such vapors being passed with the condensate downwardly through diffuser tube it. The vapors issuing into diifuser tube H; from jet nozzie 2i expand in volume and condense at least in part upon coming in contact with the relatively cooler condensate thereby serving to preheat the condensate before return to the boiler. As the condensate and vapors pass downwardly through the convergent upper portion of the diffuser tube ll, the diminishing volume'of the tube causes the fluid mixture to increase in velocity and decrease in pressure. After passing through the constricted throat of diffuser tube ll, the fluid mixture decreases in velocity and increases in pressure upon passage downwardly through the divergent lower portion of diffuser tube l? whereby condensate is forced backinto' boiler it through the second condensate conduit it against t. e pressure in the boiler. Since'the primary and secondary vapor conduits are lag fifi and the heat of the vapors impelling condensate in the condensate return means is used to preheat the condensate, there is very little loss in energy due to operation of the condensatereturn means. The pump does not depend upon a hydrostatic head of condensate for returntotthe .boiler against boiler pressure and hence the pumping apparatus, can be constructed- --velocity and hence provide greater pressure. for

returning condensate to the boiler. whereby the condensate return means is automatically responsive to pressure changes in the boiler. "The vacuum pumping apparatus embodying the invention can thereby be operated at'high boiler:

pressures resulting in an increased pumping rate and the ability to operate against a higher-forepressure. j

While the invention has; been described inconsiderable detail with reference to a preferred embodiment thereof, it will be understoodthat variations and modifications can be fifififite-d in t a a u od in h i ventionw thi the spirit and scope of the invention'as illustrated in the drawing and described he reinaboue and as defined in the appended claims.

What We claim is:

1 Vacuum pumping wherein organic pump fluid vapors are passed through paired ejector and diffuser elementsiand a rat s. of the-typ V condensed, said apparatus comprising in combination vacuum pumping means including paired ejector and diifuser elements, a boiler positioned below and spaced from said vacuum pumping means, vapor-channeling means connecting said boiler and said ejector element, and means for returning condensate from said pumping means to said boiler against pressure in said boiler, said means for returning condensate comprising a downwardly directed diffuser tube between said pumping means and said boiler, a condensate return conduit connecting said pumping means with an upper portion of said diffuser tube, a second conduit connecting a lower portion of said diffuser tube with said boiler in a lower zone of said boiler below the normal liquid level in said boiler, jet nozzle means directed downwardly into said diffuser tube, and a vapor conduit connecting said jet nozzle means and said vapor-channeling means.

2. Vacuum pumping apparatus of the type wherein organic pump fluid vapors are passed through paired ejector and diffuser elements and condensed, said apparatus comprising in combination vacuum pumping means including an ejector element and a diffuser element arranged in pumping relation, said pumping means having an inlet port in a low pressure zone of said pumping means and having an exhaust port in a higher pressure zone of said pumping means, condenser means arranged in heat-conducting relation with said difiuser element and arranged for condensing organic pump fluid vapors passing through said diflfuser element, a boiler positioned below and spaced from said pumping means, a primary vapor conduit connecting said boiler and said ejector element, and means for returning condensed pump fluid from said pumping means to said boiler against pressure in said boiler, said means for returning condensed pump fluid comprising a downwardly directed diffuser tube disposed between said pumping means and said boiler, said diffuser tube including a downwardly converging upper portion and a downwardly diverging lower portion, a condensate return conduit connecting said pumping means with said upper portion of said diffuser tube, a second conduit connecting said lower portion of said diffuser tube with said boiler, jet nozzle means directed downwardly into said upper portion of said diffuser tube, said condensate return conduit being connected to said diffuser tube at a zone not lower than said jet nozzle means, and a secondary vapor conduit of substantially a lesser cross-section than said primary vapor conduit and connecting said jet nozzle means and said primary vapor conduit.

3. Vacuum pumping apparatus of the type wherein organic pump fluid vapors are passed through ejector and diffuser elements arranged in pumping relation and condensed, said apparatus comprising in combination a generally horizontally disposed diffuser element having a convergent low pressure portion and a divergent high pressure portion, an ejector element directed into said convergent low pressure portion, a boiler spaced from and below said diffuser element, a primary vaporconduit connecting said boiler with said ejector element, an inlet port in the low pressure portion of said diffuser element, an outlet port in the high, pressure portion of said diifuser element, a condenser coil. for carrying cooling fluid disposed around said diffuser element in heat-conducting relation therewith, and means for returning condensed pump fluid from said diffuser element to said boiler against pressure in said boiler, said means comprising a generally vertically disposed diffuser tube positioned below said diffuser element and above said boiler and having a downwardly convergent upper portion and a downwardly divergent lower portion, a condensate conduit connecting said diffuser tube with said upper portion of said diffuser tube, a second condensate conduit connesting said lower portion of said diffuser tube with said boiler in a zone of said boiler below the normal liquid level in said boiler, a flared nozzle directed downwardly into said convergent upper portion of said diffuser tube, and a secondary vapor conduit of substantially lesser diameter than said primary vapor conduit connecting said flared nozzle with said primary vapor conduit, said first-named condensate conduit being connected to said diffuser tube at a zone not lower than said flared nozzle.

JUDD H. BLACK, HORACE G. WARREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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