US2691481A - Vacuum pumping apparatus - Google Patents

Description

Oct. 12, 1954 SIMPSON 2,691,481

VACUUM PUMPING APPARATUS Filed June 19, 1951 2 Sheets-Sheet l INVENTOR. KENNETH M. SIMPSON ATTORNEY 1954 K. M. SIMPSON VACUUM PUMPING APPARATUS 2 Sheets-Sheet 2 Filed June 19. 1951 INVENTOR. KENNETH M. SIMPSON ATTORNEY Patented Oct. 12, 1954 UNITED STATES PATENT OFFICE VACUUM PUMPING APPARATUS.

Commission Application June 19, 1951, Serial No. 232,267

16 Claims.

This invention relates to apparatus for producing high vacua, of the type often called diffusion pumps, but more properly known as vapor-stream pumps. As is well known from the original work of Gaede and the later developments by Langmuir and others, the vapor-stream pump operates by entrainment of gas molecules from the chamber to be evacuated in a stream of vapor directed away from the chamber, thereby imparting velocity to the gas molecules in a direction toward an exhaust vent; the vapor-stream is then condensed in a cooling section of the pump to prevent its returning to the high vacuum side, and sent back to the vaporization chamber or boiler for re-use.

Materials which have been successfully used as vapor producers are mercury, various phthalic and sebacic esters, certain hydrocarbon oils sold under such trade names as Apiezon and Litton oil, and other substances of satisfactorily low vapor pressures. A rough vacuum is first produced in the chamber by such means as a mechanical pump;

the vapor-stream pump is then started, and is capable of producing vacua of the order of mm. of mercury or better. 1

Previous pumps of the vapor-stream type have been of cylindrical shape, having an outer shell, an internal chimney concentric therewith and communicating at the bottom with a boiler, and one or more batiies so disposed as to direct the updraft of vapor through the central chimney downward and against the outer cylindrical shell at an angle. The ultimate size, and hence the pumping capacity, of pumps of this type is limited by the ratio of the allowable distance between the chimney wall and the cylindrical shell surrounding it, to the diameter of the chimney. Since the jets are circular in form around the chimney, the only way to increase their length, and thereby the pumping speed, is to increase the diameter of the pump. To do so, however, means that for each increase in the length of the jets by means of increased diameter, the cross-section of the chimney is increased by the square of the amount of jet-length increase. Since the eifective operation of the pump depends on the optimum flow of gas angularly across the annular space between the chimney and the outer shell, it is obvious that indefinite increase of diameter would finally produce a pump in which the chimney would occupy a disproportionately large part of the interior volume, and it would no longer be possible to drive vapor through the chimney at a rate such as to produce an optimum flow through the jets; furthermore, a large amount of the vapor 2 would be likely to condense upon the inner wall of the chimney and flow downward without having performed any pumping action at all. This practical limitation on pump size has previously required that for large pumping capacity a plurality of pumping units had to be provided.

The present invention overcomes the limitations of the prior art by using an outer shell of rectangular cross-section at the plane in which the conventional pump is circular, by elimination of the central chimney, and by using vapor jet nozzles of new and. improved design consonant with the improved configuration of the shell.

It is therefore an object of the present invention to provide an efficient vacuum pump of the vapor-stream type in which the length of the discharge jets is increased.

It is a further object of this invention to provide a vacuum pump in which the length of the discharge jets is increased without increasing the distance between the jets and the outer wall.

Yet another object of the present invention is to provide a pumping mechanism of the vaporstream type in which the central chimney is eliminated.

A further object of this invention is to provide a pumping mechanism in which the discharge jets have adjustable apertures.

A still further object of this invention is to provide a pumping mechanism with high pumping speed without a plurality of pumping units.

Other objects and advantages of the invention will appear hereinafter.

The invention will be more clearly understood from the following description in which are set forth two ofthe preferred embodiments for purposes of illustration but not as a limitation thereof, and from the accompanying drawings, wherein like numerals refer to like parts, and wherein Figure 1 is an elevational view, mainly in crosssection, of the improved vacuum pump;

Figure 2 is a sectional plan view taken on the line 2-2 of Fig. 1;

Figure 3 is an enlarged view showing the method of mounting the jet nozzles within the pump of Fig. 1;

Figure 4 is an enlarged sectional view of one type of jet nozzle, taken on the line 44 of Fig. 3;

Figure 5 is an enlarged sectional view of another type of jet nozzle, taken on the line 5-5 of Fig. 1.

Figure 6 is a general utility view of a plurality of the novel pumps of Fig. 1, mounted on the wall of a large vacuum chamber;

Figure 7 is a plan view of another embodiment of the present invention;

Figure 8 is a sectional elevation taken on the line 88 of Fig. '7; and

Figure 9 is an end elevation indicated by the arrow 9 of Fig. 8.

Referring to Figs. 1-5 of the drawing and more particularly to Fig. 1, there is shown a portion of a vacuum vessel l 1 having sealed about an opening in a wall thereof, as by welding, a rectangular manifold i2 provided with an outwardly projecting rectangular flange I3 surrounding the orifice thereof. A generally rectangular, vertically disposed vessel 16 comprising the external shell of the pumping apparatus is open along one side, the open side being provided with an outwardly projecting rectangular flange It adapted to mate with the flange I3 and to be attached thereto as by bolts or other convenient means, with gas ket material IE! or other suitable sealing means therebetween.

The vessel I6 is comprised of a top wall l'i and a bottom wall l8 spaced apart by side walls I9 and 2! substantially parallel in the vertical direction; to provide a suitably configured passage through the vessel 16, the side walls [9 and 2i are disposed substantially parallel in the horizontal direction for approximately the first third of their lateral extension, then they turn angularly inward to approach each other during approximately another third of their lateral extension, then they become horizontally parallel again throughout approximately the last third of such lateral extension, the space between said side walls then being about one-third or less of the space therebetween at the widest portion, or throat-section, of the vessel It.

The bottom wall I8 is provided with an aperture 22 of suitable size and configuration for the introduction of jet nozzles presently to be described, said wall slanting downward angularly from the throat section of the shell to provide drainage for oil or other fluid pumping agent which condenses on the side walls and runs to the bottom of the chamber. The top wall I! may be parallel with the bottom wall, as shown in Fig. 1, although it is to be understood that no limitation is intended by such configuration. The extended narrower side of the vessel It, or high pressure section, terminates in an exhaust flue 2d of generally tubular or other convenient shape communicating at the bottom thereof with a fluid return tube 26, the other end of which tube communicates with the interior of a boiler 21 (shown schematically in Fig. l) in which the pumping fluid is vaporized, the tube 25 entering the boiler at a point below the level of the fluid therein.

In the present embodiment the apparatus is preferably equipped with three jet nozzles, although it will be readily understood that the device will operate successfully with a greater or less number of such nozzles. A nozzle 31 occupies a vertical position in the narrower, or high pressure, section of the vessel [6 midway between the side walls 19 and 2i and parallel therewith; a nozzle 32 stands vertically in the mid-pressure region of the vessel l6 midway between the side walls at the portion where said side walls approach each other angularly; and a nozzle 33 stands vertically in the low pressure or widest F region of the vessel l6 parallel with the side walls and midway therebetween. Vapor from the boiler 2? is fed to the nozzle 3| by a duct 4| communicating with said boiler; a duct 42 communieating with the boiler feeds the nozzle 32; and- 4 the nozzle 33 is fed by a duct 43 communicating with the boiler. The ducts 4 l 42, and d3 are provided with individual valves 4%, 45, and t6 respectively, whereby the flow of vapor in each duct may be controlled independently of the flow in the other ducts. The aperture 22 in the bottom wall 13 of the vessel 16 is sealed by a closure plate 23 secured to the bottom wall by bolts 25 or other convenient fastening means and having gasket material 20 or other suitable sealing means between the wall [8 and the plate 23, said closure plate being transpierced in a gas-tight manner by the vapor ducts M, 4 2, and G3. Tubing 36 may be disposed on the exterior surface of the vessel 18 to provide water circulation for additional cooling for the condensation of vapor, although the pump will operate without such added cooling means.

To prevent backward diffusion of pumping fluid into the vacuum chamber, a vertical flat baiile plate 37, as illustrated in Fig. 2, extending from the bottom Wall l8 of the vessel 16 to the top wall I? and having a width slightly more than one-third of the distance between the side walls I9 and 2 is disposed within the throat of the vessel perpendicularly to the direction of air intake and substantially centered between the side walls of the vessel. Vertical flat balile plates 38 and 39 extend from the side walls of the vessel It toward the center thereof and from the bottom wall lil to the top wall H, and are positioned in the throat of the vessel between the central bafile plate 37 and the vacuum chamber. Each of the side baiiie plates 38 and 39 has a width of approximately onethird of the distance between the side walls of the vessel, and projects inwardly with the inner edge thereof turned slightly downstream from its point of attachment to the side wall, so as to provide less obstruction to gas flow than would be the case in directly perpendicular placing. The three baffles 37, 38, and 39 are thus so placed as to occlude the direct line of sight between any of the jet nozzles SI, 32, and 33 and the vacuum chamber, but still allowing gas flow therebetween, their purpose being to serve as surfaces against which will impinge any vapor molecules or particles emitted from the jet nozzles with a backward component of velocity. Such backwardly directed vapor will condense on the baffle plates and eventually return to the boiler through the drainage system provided by the slanting bottom wall 13 and return tube 26. It will be understood that any other arrangement of baflles occluding the direct line of sight will serve the same purpose; the pump may also be operated without such bafiling, although its efficiency is increased thereby.

The vapor ducts 32 and i3 terminate within the vessel it] near the bottom thereof, as illustrated in Fig. 3, and are each provided with an annular flange 48 surrounding the duct near the termination thereof within the vessel. An elongated generally tubular member 39 of inside diameter providing a slip fit with the outer diameter of the duct 52 (or of the duct 33 which has an identical termination within the vessel I5) and having a longitudinal slit along the entire length thereof rests vertically on the flange 48, being slidably engaged with the duct portion which extends above said flange. The top end of the tube 49 is sealed with a closure plate 5! having protruding upwardly therefrom a pin 52 engaged with a socket 55 in the top wall ll of the vessel l6.

- means for jet vanes 56 and and to prevent the entrance of gas to the jet section between the vanes from the bottom. Plate 53, as shown in Fig. 4, extends approximately from the vertical or longitudinal axis of the tube 49 to a point well outside thereof in the direction of gas flow through the jet; said plate passes transversely through the open slit of tube 49 at the bottom thereof, the slit being enlarged at that portion to accommodate the width of the plate, and the walls of the tube being attached in a gas-tight manner to the edges of the plate at the point of contact. The upper ends of ducts 42 and 43 are also cut out to accommodate'the width of each plate 53, which lies transversely across the fiange 48, being supported thereby, and forming a locking arrangement in the slot of the duct to prevent turning of the nozzle tube.

Vertically positioned and supported on the plate 53 are the aforesaid jet vanes 55 and 51 comprising a pair of planiform members parallel with the longitudinal axis of the tube 49 and extending from a point approximately at the center of said tube through the open wall thereof and outwardly therefrom for a distance approximately equal to the radius of the tube, said vanes diverging angularly from their portion of greatest propinquity within the tube to their portion of greatest separation outside the tube, thus forming a nozzle tapering in cross-section and of considerable length in the vertical dimension, for the discharge of gas fed into the tube from the gas duct 42. The edges of the tube 49 at the open slit are recurved or turned back to form extending lips 56 parallel to the vanes 56 and 5'! and secured to the outer surfaces thereof, as by screws 59 or other suitable means.

The vane 56 is a fixed vane and its position relative to the plate 53 and the tube 49 is nonadjustable; its position is determined by a pin 5|, seated vertically in the closure plate 5| and projecting downwardly into a socket formed in the end edge of said vane, and by a similar pin 62, likewise seated vertically in the plate 5| and projecting downwardly into a second socket formed at a second point in the end edge of the vane 56; the lower end of said vane is secured in a similar manner by like pins BI and 62' seated in ,the plate 53 and projecting upwardly into appropriate sockets formed in the lower end edge of the vane 56. It will be understood that firm positioning of the fixed vane 56 may also be obtained by welding, soldering, clamping, bolting, or other means.

The vane 5'! is adjustable angularly with respect to the vane 56; a pin 63 is vertically seated in the closure plate 5i and projects downwardly into a socket formed in the upper end edge of the adjustable vane 51 at a point near the center of the width thereof; a like pin coaxial with pin 53 is seated in the plate 53 and projects upwardly into a socket formed in the lower end edge of the adjustable vane, the upper and lower pins comprising a pair of trunnions about the axis of which the vane may be swung. Two vertically spaced internally threaded nuts 66 are mounted on the rear edge of the adjustable vane 51 within the tube. Threadably engaged with said nuts are adjusting screws 6! extending normally to the bisector of the angle formed by the two vanes, outwardly through the wall of the tube and through screw-retainer blocks 68 mounted on 'the'wall of the tube 49 and provided with clearance holes for the passage of the screws. The screws 6'! are provided with enlarged shaft- .sections 69 inside the tube to prevent backing the screws out through the retainer blocks, and large head sections H to bear against the out side of the retainer blocks when adjustments are made. It is therefore apparent that when the adjusting screws are turned the threaded section pulls or pushes upon the nuts'BS, thereby rotating the vane 51 about the axis provided by the trunnion pins to. open or close the angle of the jet discharge between the vane 5'! and the vane 56.

Another type of jet nozzle 3|, as illustrated in Fig. 5, may be mounted in the high pressure section of the pump in lieu of the nozzles 32 and 33 previously described. A generally tubular member (6 having a longitudinal opening in the wall thereof has the wall edges turned back from said opening and prolonged to form extended lips ll along the opening, giving a keyhole shape to the transverse section of the tube. The tube 76 is open at the bottom end and rests on the flange 56 of the duct 4|, having a slip fit over the open upper end of the duct; the tube is closed at the top end by a closure plate '58. The lips ll comprise the outer wall of the jet portion of the nozzle 3|, and are of such size and extension as to bring them .close to the vessel walls i9 and 25 when the nozzle is installed on the centerline of the high pressure section of the vessel 16; top and bottom end plates 19 joined in a gastight manner to the lips 17 complete therewith a four-sided outer jet wall, the top and bottom plates being respectively slanted toward the top and bottom walls of the vessel in such a manner as to allow the gas discharge from the jet to strike the top and bottom vessel walls. A plurality of studs 81 is borne by the wall of the tube 16, extending across the interior diameter thereof transversely of the longitudinal axis and pro jecting through the opening in the wall thereof substantially centrally between the lips T1, the free ends of said studs being tapped. Mounted on such studs 8| and positioned thereby is a trough-like member 82 having two sides substantially parallel to the lips TI and two sides substantially parallel to the plates 19, and a fifth side suitably apertured for screws 83 by which it is retained on the said stubs. Thus the aperture between lips I? is restricted to a rectangular slit having the angle of discharge of each of its four sides directed outwardly.

It will be apparent from the foregoing that a vacuum chamber of very large size may be readily exhausted by a single pump, or more rapidly by a plurality of pumps 16, as illustrated in Fig. 6. In such application, a plurality of pumps may be provided with a common boiler 21, as shown, or each pump may have its individual boiler. When a common boiler is used, separate duct and valve means for each set of like nozzles within the pumps may be provided, as shown in Fig. 6, although one or more pumps may be successfully operated with a single boiler connection for all nozzles. An electrical input conduit 86 to the boiler is provided for heating thereof, or if de sired other conventional heating means may be employed, such as gas, oil, or other fuel. Pumping oil, or other fluid of suitable characteristics, for the first filling or for make-up may be introduced through a boiler intake 87. Booster diffusion pumps 88 of conventional design and lower speed than the improved pump herein described, 5

but capable of maintaining a relatively higher discharge pressure, receive the discharge from the exhaust ilues 24 and pass it to an exhaust line 89, whence it passes to the mechanical backing pumps which discharge it to air.

In the evacuation of a large vacuum system the normal sequence of operations would be as follows: First the rough vacuum is drawn by operation of the backing pumps, usually mechanical, through the pumping system without using the difiusion pumps, the backing pumps being disposed in the exhaust system beyond the booster difiusion pumps. The gas to be exhausted from the vacuum vessel moves by viscous flow through the manifold to which the pump of the present invention is connected, past the baffles 37, 33, and 39 in an undulant path, through the chamber of the novel pump which is not yet in operation, through the exhaust flue and on through the exhaust system, from which it is discharged to the atmosphere by the backing pump. When a satisfactory rough vacuum has been obtained, the booster difiusion pump is started, and the pressure further reduced.

The valve M of the present invention is then opened, whereby vapor is supplied to nozzle 3! in the high pressure region of the pumping chamber; as the pressure further decreases, the valve 45 is opened, supplying vapor to nozzle 32 in the mid-pressure region, and then the valve 45, supplying vapor to nozzle 33 in the region of lowest pressure.

When the improved pump is in full operation, the gas pressure in the vacuum vessel has been reduced to where the gas no longer moves by viscous flow, but enters the vapor-stream by the random movement of gas molecules according to the kinetic theory of gases at low pressure. Gas molecules entering the vapor-stream are given a component of velocity in the direction of the stream by entrainment or by the imparting of the momentum of the vapor-stream to the gas-molecules, the vapor-stream subsequently being condensed and returned to the boiler.

The booster diiiusion pumps may be omitted from the system if desired, and all jets of the present pumping apparatus may be opened simultaneously; a separate boiler for each pump may be provided, or a central boiler for a plurality of pumps.

A second preferred embodiment of the present invention, as illustrated in Figs. 7-9, inclusive, provides a pump structure which is useful in those instances where it may be desirable to install the pump with its major dimension horizontal instead of vertical. In such an installation the major changes involved are in the horizontal suspension of the jet nozzles and in the configuration of the shell. The same type of mountings for the nozzles may be used as those previously described for vertical placement, and one of the large walls of the pump, which becomes a bottom wall, may be slanted downward to provide for oil drainage. Thus, as shown in Fig. '7 a vacuum vessel H has a rectangular manifold 12 sealed about an openin in the wall of said vessel, with an outwardly projecting rectangular flange 13 surrounding the orifice of said manifold. A generally rectangular horizontally disposed vessel 3| comprising the external shell of the pumping apparatus is open along one side, the open side being provided with an outwardly projecting rectangular flange It adapted to mate with the flange i3 and to be secured in a gas-tight manner thereto as by bolts 15 or other convenient means, with gasket material 10 or other suitable sealing means therebetween. Positioned within the shell are three jet nozzles 31, 32, and 33, of the design already described, supported on the same type of mountings as in the previous embodiment, and supplied by gas ducts ll, 32, and 43, respectively.

One of the broad walls of the vessel 9!, as illustrated in Fig. 8, serves as a bottom wall 92 which is flat and slanted slightly downward toward the drain tube 26. The other broad wall comprises a top wall 93, substantially parallel to the bottom wall for approximately the first third of its lateral extension from the vacuum vessel H, then turnin downwardly to approach the bottom wall angularly in the approximate central region of the vessel 9!, thus providing the constriction required for satisfactory operation, then again be coming parallel with the bottom wall 92 in approximately the last third of its extension, comprising the narrow or h gh p s region of the vessel ill.

The jet nozzle 33 is positioned midway between the top wall 93 and the bottom wall 92 and havin its longitudinal axis parallel therewith in the low pressure region of the vessel GI and discharges in a direction substantially parallel with said walls; the jet nozzle 32 is disposed midway between the top and bottom walls and having its longitudinal axis substantially parallel therewith at the portion where the top wall 93 angularly approaches the bottom wall 92, the nozzle 32 be ing positioned to discharge along the bisector of the angle between said top and bottom walls; and the jet nozzle Si is disposed midway between the top and bottom walls and parallel therewith in the high pressure region of the vessel 9! and discharges substantially parallel with the walls. The exhaust flue 24 at the high pressure region communicates with an exhaust system suchas described in the previous embodiment.

Although it has been found convenient to illustrate the novel pumping apparatus as having three jet nozzles, the precise number of jets has no particular significance, since pumping will occur with only one or two jets operating, and a pump of this type with a larger number of nozzles may be successfully operated. It will also be apparent that although two types of jet nozzles have been shown for differing pressure conditions within the pump, the apparatus could be effectively used with nozzles of either of the types illustrated. Notwithstanding the illustration herein of apparatus with side walls which mutually turn inward to approach each other, it is obvious that convergence of the walls by any means, whether by turnin or slanting one or the other, or by the use of internal bafiies, will achieve the same degree of constriction of the space therebetween.

It is evident that the pumping capacity of the device of the present invention is not limited by a diameter, as in the previous type of diffusion pumps, since in the pump herein disclosed the .iet length, and hence the pumping capacity, may be increased to any desired length by merely extending the pump structure. Such extension does not have the disadvantage which increasing the shell diameter of the older pumps would have, of simultaneously increasing either the diameter of the central chimney or of increasing the distance between the jets and the outer shell, since the present invention eliminates the central chimney, and the linear configuration permits maintaining a constant distance between jets and shell. Thus a single pump of large size may be made to do the 9 work of many of the cylindrical pumps. The rectilinear structure of the new jet nozzles herein disclosed permits adjustment of the jets to the optimum angle of discharge, contributing to efficiency of operation in a manner heretofore unknown.

While the present invention has been described in detail with respect to two embodiments thereof, it will, of course, be apparent that numerous modifications may be made within the spirit and scope of the invention, and it is therefore not desired to limit the invention to the exact details shown, except insofar as they are defined in the following claims.

What is claimed is:

1. In a jet nozzle for a vacuum pump, the combination comprising a straight, tubular member having the wall thereof longitudinally split along a line parallel to the longitudinal axis .of said tube to provide a gap oi uniform width between the tube edges established by said line of sepa ration, a pair of vanes disposed in fixed, parallel relation with the longitudinal axis of said tube and extending from the internal portion of said tube through said open side and externally thereof, said vanes being in relatively close juxtaposition within said tube and diverging outwardly, and a closure plate disposed in sealing .relation across one end of said tubular member.

2. A jet nozzle as in claim 1, wherein the angle between said vanes is adjustable.

3. A jet nozzle as in claim 1, wherein one of said vanes is pivotally mounted with respect to said tube and said other vane and on an axis parallel to the axis of said tube, and means connected to the end of said pivotally mounted vane disposed within said tube for turning the latter vane about said axis.

4. A jet nozzle for a vacuum pump comprising a straight tubular member having a longitudinally interrupted wall portion providing a gap uniform in width and of substantial length, a pair of outwardly diverging planar lips integral with the gap-defining edges of said wall portion and serving to radially define said gap with reference to said tubular member, and a baffle comprising a. trough-like member having a wall substantially parallel with one of said lips and in relatively close juxtaposition thereto, a second wall substantially parallel with the other of said lips and in relatively close juxtaposition thereto, and a third wall disposed substantially normal to the biscctor of the angle between said lips, and a closure plate disposed in sealing relation across one end of said tubular member.

5. A vacuum pump of the vapor-stream type comprising in combination a pumping vessel of generally rectangular cross-section having two opposite open sides, the first open side being adapted to be attached to a vacuum vessel in communication therewith, a bottom wall slanting downward from the said vacuum vessel toward the said second open side, a top wall converging toward said bottom wall from the said first open side toward the said second open side, a pair of side walls spaced apart by said top and bottom walls, an exhaust flue hermetically sealed to said pumping vessel and communicatin with the interior thereof at the said second open side, a generally tubular nozzle extending inwardly from one of said walls and horizontally disposed within said pumping vessel midway between said top Wall and said bottom wall, said nozzle being open along a major portion of its length on the side opposite said vacuum vessel a nd adapted to dis- 10 charge fluid toward said exhaust due. a source of fluid communicating. with one end of said nozzle, a closure for the other end of said nozzle, and a generally tubular member communicating with the interior of said pumping vessel at its lowest portion and with said source of fluid.

'6. A vacuum pump as in claim .5, wherein the walls thereof are provided with cooling means comprising a tube in thermal contact with the walls of said pump, Said tube communicating with a source of cooling fluid.

7. A vacuum pump as in claim 5, wherein the distance between said top and bottom walls at the converged portion thereof is less than one-half the distance between said walls at the unconverged portion thereof.

8. A vacuum pump of the vapor-stream type comprising in combination a pumping vessel of generally rectangular cross-section having two opposite open sides, the first open side being adapted to be attached to a vacuum vessel in communication therewith, a bottom wall slanting downward from the said first open side toward the said second open side, a top wall converging toward said bottom wall from the said first open side toward the said second open side, a pair of side walls spaced apart by said top and bottom walls, an exhaust flue hermetically sealed to said pumping vessel and communicating with the interior thereof at the said second open side, a plurality of spaced apart, generally tubular nozzles extending inwardly from one of said walls and disposedinparallelism with said bottom wall and with each other and normally intersecting a median line defined as extending between said open sides and also lying between said top wall and said bottom wall and equidistant from said side walls, each of said nozzles being open along a major portion ofits length on the side opposite said vacuum vessel-and'adapted to discharge fluid toward said exhaust flue, .a source of fluid com- .municating with one ,end of said nozzles and a closure for the other ends of said nozzles, and a generally tubular member communicating with the interior of said pumping vessel at its lowest portion and with said source of fluid.

9. A vacuum pump of the vapor-stream type comprising in combination a pumping vessel of generally rectangular cross-section having two opposite open sides, one open side being adapted to be attached to the vacuum vessel in communication therewith, an exhaust flue in hermetically sealed relation with said pumping vessel and in communication with the interior thereof at the second open side, at least one jet nozzle vertically extended within said pumping vessel and comprising a generally tubular member open along one side thereof and having a pair of vanes disposed in parallelism with the longitudinal axis of said tube and extending from a closely juxtaposed position internally of said tube through said open side to a position of divergence externally of said tube, a jet nozzle r vertically extended within said pumping vessel,.

parallel to said first nozzle and spaced therefrom in the direction of said exhaust flue and comprising a generally tubular member open along one side thereof and having the open edges thereof prolonged into a pair of lips diverging outwardly from said tube and having disposed between said lips a baffle comprising a troughlike member having a wall substantially parallel with one of said lips and in relatively close juxtaposition thereto and having a second wall substantially parallel with the other of said lips and in relatively close juxtaposition thereto and having a third wall disposed substantially normal to the bisector of the angle between said lips, a source of fluid communicating with one end of said nozzles, and a closure plate disposed in sealing relation across the other ends of said tubular members.

10. A vacuum pump of the vapor-stream type comprising in combination an open-ended pumping vessel of generally rectangular cross-section and defined by pairs of oppositely disposed lateral walls, one of said open ends being adapted to be attached to a vacuum vessel in communication therewith, an exhaust flue hermetically sealed across the opposite end of said vessel, a generally tubular jet nozzle extending inwardly of said vessel through a wall thereof across the major lateral extent of said vessel and equally spaced from a pair of oppositely disposed lateral walls, said nozzle having an opening directed toward said exhaust flue and extending for a major portion of the length of said nozzle, a source of fluid supply connected to one end of said nozzle, and a closure plate disposed in sealing relation across the other ends of said tubular member.

11. A vacuum pump as in claim 10 wherein the walls thereof are provided with cooling means.

12. A vacuum pump as defined in claim 10, and wherein one of said first-mentioned walls serves as a bottom wall and connects said last-mentioned pair of walls, said one wall being slanted downward from said one end of said vessel toward said opposite end thereof, and a fluid conduit connecting the lowermost portion of said slanted wall and said source.

13. A vacuum pump as defined in claim 10 and wherein a tube in thermal contact with a plurality of said walls and connected to a source of cooling fluid serves to cool said pump.

14. A vacuum pump as defined in claim 10 and wherein said latter pair of oppositely dis- 12 posed lateral walls converge between said open ends of said vessel.

15. A vacuum pump as defined in claim 10 and wherein said latter pair of oppositely disposed lateral walls converge between said open ends of said vessel to a spacing which is less than one-half the spacing thereof in the unconverged portion of said pumping vessel.

16. A vacuum pump of the vapor-stream type comprising in combination an open-ended pumping vessel of generally rectangular cross-section and defined by pairs of oppositely disposed lateral walls, one of said open ends being adapted to be attached to a vacuum vessel in communication therewith, an exhaust flue hermetically sealed across the opposite open end of said vessel, a plurality of generally tubular jet nozzles spaced apart along a line connecting the open ends of said vessel and extending inwardly of said vessel through a wall thereof across the major lateral extent of said vessel and equally spaced from a pair of oppositely disposed lateral walls, said nozzles having openings directed toward said exhaust flue and extending for a major portion of the length of said nozzles, a source of flue supply connected to one end of said nozzles, and a closure plate disposed in sealing relation across the other ends of said tubular members.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 927,449 Carnaham July 6, 1900 1,759,920 Talbott May 27, 193.0 2,080,421 Hickman May 18, 193'? 2,153,189 Hickman Apr. 4, 1939 2,314,078 Crawford Mar. 16, 1943 2,390,814 Stallman Dec. 11, 1945 2,568,492 Gallick Sept. 18, 1951

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