US2336764A - Pump - Google Patents

Description

Patented Dec. 14, 1943 UNITED STATES PATENT oFricE PUMP Frank R. Abbott, San Diego, Calif., assignor to 'General Electric X-Ray Corporation, Chicago,

111., a corporation of New York Application April 8, 1942, Serial No. 438,151

9 Claims.

My invention relates in general to pumping and has more particular reference to pumping for the production of extremely low pressure, the invention pertaining especially to the production of vacuum conditions by difiusion pumping.

An important object of the invention is to provide an improved diifusion pump characterized by the absence of activated charcoal and liquid air traps heretofore considered essential in diffusion pumps, thus eliminating the necessity of frequent maintenance operations required to keep the trap in serviceable condition.

Another important object is to provide suitable apparatus for vaporizing the pumping medium, directing the vapor as a pumping jet, and condensing the vapor and recirculating the condensecl medium for repetition of the pumping cycle, while maintaining the pumping medium at the necessary temperatures required at the various stages in the pumping cycle.

Another important object is to provide an improved jet structure for use in a diiiusion pump; a further object being to utilize an annular jet arrangement; a, still further object being to utilize lava or similar refractory material in forming a jet nozzle for adiffusion pump.

Another important object is to provide a diffusion pump wherein the pumping medium is fvaporized by an electric are maintained between a suitable anodeand pumping medium in molten condition as a cathode; a further object being to utilize a tungsten anode for the establishment of the heating are; a further important object being to utilize aluminum oxide or other inert material as a crucible or container for supporting the liquid pumping medium in position to form an arcing cathode.

Another important object is to provide improved means for adjusting the arcing anode in the pump; a further object being to provide means for maintaining the anode at a desired temperature during the operation of the pump. Another important object is to provide means for sealing the pump against th escape of pressure at the place where the anode adjusting means extends outwardly of the pump casing, Another important object is to provide a diffusion pump having a heating chamber for the evaporation of a heating medium, including means preferably forming an evacuated jacket around said heating chamber in order to minimize heat loss outwardy of said chamber, thereby improving the efficiency of the pump.

Another. important object is to provide a diffusion pump having means for evaporating the pumping medium by resistance heating; a further object being to utilize a column of molten pumping medium as the resistance heater and to provide means for passing an electrical curably copper plated, as a seal between the heater and jet sections of the pump housing.

Another important object is to form the heater section as a, casing of steel, preferably a seamless steel tube containing a liner for defining a heating chamber for the pumping medium, opening to a jet nozzle located in a jet chamber forming part of the jet housing, the jet chamber communicating with a pumping chamber and also with a condensation space formed in the heater section of the pump housing; a further important object being to provide a pump comprising parts of simple form readily produced and easily assembled.

Another important object is to provide a pump structure which may be used as a pump operated by a resistance heater or by an arc heater merely by assembling the appropriate heater section in the pump structure.

These and numerous other important objects, advantages, and inherent functions of the invention will be fully understood from the following description, which, taken in connection with the accompanying drawing, discloses preferred embodiments of the invention.

Referring to the drawing:

Figure 1 is a sectional view taken through a diffusion pump operated by an arc; and

Figure 2 is a sectional view through the lower portions of a diffusion pump embodying a resistance heater.

To illustrate the invention, I have shown on the drawing diffusion pumps, each comprising a housing forming a vaporizing chamber ll communicating upwardly with a jet nozzle l3 preferably designed to project annular jets downwardly into an annular condensing chamber [5 which surrounds thevaporizing chamber- II.

The condensing chamber l5 comprises cornmunicating cavities formed, respectively, in the end of a section I! comprising the heating section of the pump housingand in a head I9 comprising the jet section of the housing, the jet nozzle l3 being located within the upper portions of the head l9 remote from the section H. The section l'l may comprise a tube having a flanged open end adapted to be secured, as by bolts, to the head IS. A sealing gasket l8 preferably of soft iron coated with copper y be ed at the joint to seal the same, sort iron being particularly well suited to maintain a tight joint between the head IQ and the section I! through therange of operating temperature involved.

The head I! preferably comprises a block oi steel having therein the cavity forming the upper portion of the condensing' chamber I5, said cavity communicating upwardly of the jet nozzle I3 with a pumping chamber 2I through an opening 23 forming a continuation of the chamber I5. The walls of the pumping chamber 2| may be formed in any suitable or preferred fashion, as by means of a glass sleeve 25, the opposite annular edges of which form glass-to-metal seals 21 with an annular preferably steel disk or washer 2!! formed withacentral opening. The edges of the central'opening of one of the disks 29 are brazed or otherwise sealingly secured, as at 3|, upon the upper side of the head I3 around the opening 23, the central opening of the other disk being sealingly secured in like fashion to the end of a pumping head 35 comprising, in the illustrated embodiment, a cup-like element having a cavity 31 in open communication with the pumping chamber 2|. The pumping head 35 is fitted with a fine vacuum connection comprising a nipple 39 which communicates with the cavity 3'! through a side wall of the head 35, the nipple 35 being connectible with any hollow envelope or casing enclosing a space to be evacuated.

The bottom of the cup-like element 35 is formed with an opening 4I through which extends a tubular anode support 43, the space between the member 43 and the edges defining the opening 4I being sealed by means of a metallic bellows 45, one end of which issealed to the head around the opening 4I and the other end of which is sealed to an annular flange 41 which, inturn, is sealed on the member 43. The bellows 45 is enclosed within and protected by a preferably steel .sleeve 49, one end of which is fastened, as by set screws, to the head 35, and the other end of which supportsa collar I which is internally threaded, as at 53, for the reception of a gland 5.5 which carries the tubular member 43 and which is formed with a manually operable head 51 to facilitate the turning of the gland 55in the collar 5I in order to raise or lower the member 43.

The end of the tubular member 43 extends within the pumping chamber 2| and carries, sealed thereto, a preferably steel block 59 forming a mounting head for an anode. This anode preferably comprises a slender rod 50 of molybdenum, which is secured at one end as by threading the same in the mounting head 58, the rod at its opposite end carrying a tip 6| of tungsten or carbon. The rod 55 is preferably provided with a thin sheath 53 of inert refractory material, such as aluminum-oxide, the sheath extending throughout the rod from the mounting head 55 to the tip N which is exposed.

The exposed and or tip 8| of the anode extends within the heating chamber I I, which comprises a cavity for the reception of a suitable pumping medium 85, which forms a molten pool in the bottom of the chamber II in position to form a cathode for co-operation with the tip of the anode. By applying a suitable electrical potential between the anode and the pool of molten pumping medium, an arc may be struck between the anode and the cathode for the purpose of vaporizing the pumping medium in the chamber II.

As shown in Figure 1, the chamber I I is defined within the casing portion H by a block 51 of inert refractory material, such as aluminumoxide. This block of material 61 is formed to fit snugly within the walls defining the housing portion II, which preferably comprises a steel tubehaving an open end adapted to be mountably secured to the head I9, as by means of the fastening bolts 59, the opposite end of the tube I'I being closed by means of a steel disk or plate II welded or otherwise sealingly secured to the lower end of the tube I I The block of refractory material BI is fitted snugly within the tube I1 and rests at its lower end upon the plate II, thus entirely filling the lower portions of the tube. The block 51 has a central cavity forming the chamber II and is cut away as at I3 to provide a cylindrical neck I5 within the upper portions of the casing section II, said neck extending into the cavity forming the chamber I5 in the head I9, thereby defining the upper portions of the vaporizing chamber within the condensing chamber I5, inwardly of the cylindrical The jet nozzle I3 comprises an annular rim 11 mounted upon the upper extremity of the neck I5, said rim preferably comprising lava or equivalent refractory material and being sealed, as by means of suitable cement, upon the sleeve-like neck I5. The rim I1 is preferably formed with upstanding fingers I9 formed at intervals around the rim for the support of anannular skirt-like nozzle element 8|, which overlies the rim I1 and is supported in place by the fingers I9 in position forming, with the rim 11, an annular jet nozzle through which vapor generated in the chamber II by the heating of the pumping medium 65 may be projected downwardly into the condensing chamber I5. The annular skirt-like nozzle member 8I preferably comprises lava or other equiv alent refractory material and is formed with a central opening through which the rod 60 extends, said rod being axially movable through said opening. Preferably, a helical spring 83 encircles the rod between the mounting head 59 and the central portions of the nozzle member 8I to yieldingly urge the same downwardly into seated position upon the supporting fingers I9.

head 35 and the nozzle element 8|.

I prefer also to enclose the mounting head 58 and the portions of the rod 50 and of the member 43 which extend in the chamber 2| between the This is accomplished by means of a sleeve 85 preferably formed of lava, which is annularly sealed at one end to the nozzle element BI and which extends at its other end to the bottom of the cup-shaped head 35 forming the cavity 31.

The lower end of the block 61 is preferably formed with an axial channel 81 for the snug reception of a pin 83, which is fastened at one end in the disk 'II and which extends at its other end within the lower portions of the chamber II in contact with the pool of pumping material 55.

The pumping medium vaporized in the chamber II is expelled from the upper end of the chamber in the form of an annular Jet through the nozzle means and passes downwardly in the condensing chamber I5. The action of the Jet produces low pressure conditions in the chamber 2| and in the vessel connected to the nipple 33. The vaporized pumping medium projected into the chamber I5 condenses therein to a molten condition and escapes thence through a return circuit to the pool 65 at the lower end of the heating chamber II. To this end, I provide a return conduit 8| connecting through the wall of the housing portion H with the lower portions of the condensing chamber I5, the conduit means 8|, at its other end, being connected.

2,336,764 through an opening in the casing portion I1 and through a duct 93 in the block 61, with the lower end of the heating chamber II. The condensation chamber I into which the pumping chamber 2| evacuates is connected with suitable exhaust discharge means, such as a mechanical exhaust pump, which may be connected with the chamber I5 through the upper portions of the conduit 8|. To this end, the conduit 9|, at its upper end, is provided with a take-off pipe 95 adapted for connection with an exhaust pump.

The heating are between the anode BI and the pool of pumping medium 65 operating as a cathode may be maintained in operation by electrical potential applied between the casing portion I1 which is electrically connected with the cathode pool by the pin 89 and the collar 5| which is electrically'connected with the anode through the mounting sleeve 43, the casing portions being electrically insulated by the glass sleeve 25.

In order to maintain the pumping chamber 2| at a desired low temperature, the anode tube 43 may be extended upwardly of the adjusting head 51 and provided with an inlet 91 through which a cooling liquid may be introduced into the sleeve 43. Within the sleeve 43 I may mount a tube 99, one end of which opens outwardly of the projecting end of the tube 43, and the other end of which opens within said tube adjacent the head 59 so that the cooling fluid introduced to the tube 43 at its projecting end will pass to the end thereof within the chamber 2|, thus conducting heat from the end of the anode rod 60 which extends in said pumping chamber to thereby maintainsaid chamber at a desired temperature of the order of 400 C., the

lava sleeve 85 serving to prevent the escape of heat from the anode into the surrounding portions of the pumping chamber;

The arrangement illustrated in Figure 2 of the drawing embodies a. modified construction of the parts forming the vaporizing chamber II, in order to provide for the vaporization of the pumping medium by resistance heating or by a combination of resistance and are heating, As

'shown in Figure 2, the vaporizing chamber II comprises a steel tube IOI carrying the annular nozzle member 11 at its upper end. The lower end of the tube IN is closed by a plug I03 sealed in said tube and carrying a downwardly extending pipe I05 of limited diameter which extends through the plug I03 and communicates with the vaporizing chamber II. The casing I1 also is extended downwardly below the disk 1| by means of an extension tube I01, the upper end of which is sealed in an opening formed in the disk 1|, the other end of the tube I01 being closed by a disk I09. The tube I05 extends within the extension I01 and opens, as at III, adjacent the disk I09. The communicating steel tubes IOI and I05 are jacketed by means of a tube II3 enclosing the tube I05, a sleeve I I5 enclosing the lower portions of the tube IN, and a tube II1 enclosing the upper portions of the tube IOI, thetubes I I3 and II1 being sealed in open communication with the opposite ends of the sleeve I I5 by means of cellars H9 and IZI, the end of the tube II3 remote from the sleeve II5 being sealed on the tube I05 near its] end III by means of a sealing collar I23, and the tube H1 being sealed to the nozzle carrying end of the tube. IOI, thus forming a sealed jacket around the connecting tubes I0| and I05, which jacket-comprises an evacuated space I25.

The sleeve II5 fits snugly within the casing to provide for the return-of pumping medium condensed in the chamber I5,'through the casing extension I01, to the lower open end III of the tube I05. The casing I1 also is provided with an exhaust connection I29 which communicates the lower portions of the condensingchamber I5 with a suitable exhaust device such as a mechanical pump. v

As in the pump structure shown in Figure 1, the pumping'medium 'forms a pool '65 in the lower portions of the vaporizing chamber II within the tube H, the pumping medium being vaporized by the application of electrical potential between the casing portions I1 or Ill! and the rod 60, the end of which may be spaced slightly above the liquid level of the pool 65 in order 'to'cause arcing for heating purposes, or a tip of the rod 60 may be immersed in the molten pool 65. In either event, resistance heating will be accomplished by the passage of electrical current between the rod 60 and the disk I09 through the column of the molten material in the .tube I05 in order to generate vapor in the chamber II for projection through'the nozzlemeans I3. The provision of an evacuated jacket space I25 around the heating chamber prevents'heat loss outwardly from the chamber and thereby materially improves the efficiency of the pump.

It is though that the invention and its numerous attendant advantages will .be-fully understood from the foregoing description, and .it is obvious that numerous changes maybe made in the form, construction and arrangement or the several parts without departing from the spirit or scope of the invention; or -sacrificinganyof its attendant advantages, the forms herein disclosed being preferred embodiments fonthe-purpose of illustrating the invention. 0

The invention is hereby claimed as follows:

1. A difiusion pump comprising means form: ing an evaporation chamber, a condensing chamber, a pumping chamber connected with the condensing chamber throughan orifice, and a vapor jet nozzle, comprising a" refractory material such as lava, connected withthe evaporation chamber and opening into said condensing chamber adjacent said orifice, said nozzle facing in a direc I tion away from said orifice whereby to reduce pressure in said pumping chamber when said nozzle is in operation; r 4 iv v 2. A difiusion pumpcempr-ising means forming an evaporation chamber, a condensing chamber, a pumping chamber connected with the condens ing chamber throughan orifice, anda vapor jet nozzle connected with the evaporation. chamber and opening into said condensing-chamber adjacent said orifice, said nozzle facing in a direction away from said orifice, said 1 evaporation chamber comprising a member having a sleevelike portion extending ill'the condensing. chamber and. means forming aheat insulating jacket around said evaporation chamberand extending.

jet nozzle connected with the evaporation chamber and opening'into saidjcondensing chamber adjacent said orifice-said nozzle facing in a direction away from said orifice; said. chambers being formed in a housing comprising a pair of spaced metal heads respectively forming a condensing head and a pumping head, the condensing chamber being formed in the condensing head and said evaporation chamber being defined by partition means extending within the condensing chamber, the pumping chamber comprising wall means on the pumping head, and means insulating the heads the one from the other.

4. A diffusion pump comprising means forming an evaporation chamber, a condensing chamber, a pumping chamber connected with the condensing chamber through an orifice, and a vapor jet nozzle connected with the evaporation chamber and opening into said condensing chamber adjacent said orifice, said nozzle facing in a direction away from said orifice, said chambers being formed in a housing comprising a pair of spaced metal heads respectively forming a condensing head and a pumping head, the condensing chamber being formed in the condensing head and said evaporation chamber being defined by partition means extending within the condensing chamber, the pumping chamber comprising wall means on the pumping head, and meansinsulating the heads the one from the other and comprising a tubular glass wall sealed at its opposite ends to the pumping and condensing heads and defining the condensing chamber on the pumping head.

5. Adifiusion pump comprising means forming an evaporation chamber, a, condensing chamber, a pumping diambr connected with the condensing chamber through an orifice, and a vapor jet nozzle connected with the evaporation chamber and opening into said condensing chamber adjacent said orifice, said nozzle facing in a direction away from said orifice, said chambers being formed in a housing comprising a pair of spaced metal heads respectively forming a condensing head and a pumping head, the condensing chamber being formed in the condensing head and said evaporation chamber being defined by partition means extending within the condensing chamber, the pumping chamber comprising wall means on the pumping head, means insulating the heads the one from the other, and electrode means on said pumping head and extending through said pumping chamber and into said evaporation chamber in position to heat an evaporable pumping medium in the evaporation chamber.

8. Adifiusion pump comprising means form- -ing an evaporation chamber, a condensing chamber, a pumping chamber connected with the condensing chamber through an orifice, and avapor ':Iet nozzle connected with the evaporation chamber and opening into said condensing chamber adjacent said orifice,'said nozzle facing in a.direction away from said orifice, said chambers be ing formed in a housing comprising a pair of spaced metal heads respectively forming a condensing head and a pumping head, the condensing chamber being formed in the condensing head and said evaporation chamber being defined by partition means extending within the con- 7. A difiusion pump comprising means forming an evaporation chamber, a condensing chamber, a pumping chamber connected with the condensing chamber through an orifice, and a vapor jet nozzle connected with the evaporation chamber and opening into said condensing chamber adjacent said orifice, said nozzle facing in a direction away from said orifice, said chambers being formed in a housing comprisinga pair of spaced metal heads respectively forming a condensing head and a pumping head, the condensing cham-' ber being formed in the condensing head and said evaporation chamber being defined by partition means extending within the condensing chamber, the pumping chamber comprising wall means on the pumping head, means insulating the heads the one from the other, electrode means on said pumping head and extending through said pumping chamber and into said evaporation chamber in position toheat an evaporable pumping medium in the evaporation chamber, means manually operable outwardly of the pumping head for adjusting the electrode means longitudinally or said pumping head, and means for hermetically sealing the electrode means where it penesaid evaporation chamber being defined by pardensing chamber, the pumping chamber comprising wall means on the pumping head, means insulating the heads the one from the other, electrode means on said pumping head and extending through said pumping chamber and into said evaporation chamber in position to heat an evaporable pumping medium in the evaporation chamber, and means manually operable outwardly of the pumping head for adjusting the electrode means longitudinally of. said pumping head.

- chamber in position tition means extending within the condensing chamber, the pumping chamber comprising wall means on the pumping head, means insulating the heads the one from the other, electrode means on said pumpinghead and extending through said pumping chamber and into said evaporation chamber in position to heat an evap-.

orable pumping medium in the evaporation chamber, and means to circulate a cooling fluid in said electrode means within said pumping chamber.

. 9. A difiusion pump comprising means formingv an evaporation chamber, a condensing chamber, a pumping chamber connected with the condens ing chamber through an orifice, and a vapor jet nozzle connected with the evaporation chamber and opening into said condensing chamber adjacent said orifice, said nozzle facing in a direction away from said orifice, said chambers being formed in a housing comprising a pair of spaced metal heads respectively forming a condensing head and*a pumping head, the condensing chamber being formed in the condensing head and said evaporation chamber being defined by partition means extending within the condensing chamber, the pumping chamber comprising wall means on the pumping head, means insulating the heads the one from the other, electrode means on said pumping head and extending through said pumping 'chamber to heat an evaporable pumping medium in the evaporation chamber, and a heat insulating sleeve encircling the electrode means in the pumping chamber.

FRANK R. ABBOTT.

and into said evaporation

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