Патент USA US2404022код для вставки
P. ALEXANDER'ETAL. VAPOR'VACUUM-PUMP OF THE'DOUBLE JET TYPE Filed May 26, 1945 // 2,404,022 2,404,022 Patented July 16, _1946 UNITED STATES PATENT OFFICE 2,404,022 VAPOR VACUUM PUMP OF THE DOUBLE JET TYPE Paul Alexander, Berkhamsted, and Cecil Whiley, London, England Application May 26, 1945, Serial No. 596,035 In Great Britain April 21, 1945 1 claim. ( Cl. 230-101) l 2 terminates above in the inlet 6 of the pump. The upper annular jet l, with annular oriñce 3 of the double jet type. is fixed on the top of the central tube 4. The Mercury is the liquid usually vaporized in Vapor vapor from the mercury in the boiler, passing pumps but other liquids, such as oils, are em up the tube 4 enters the jet 'l through holes I0 ployed. In pumps of this type mercury vapor in the central body of the jet and issues from from a mercury boiler ascends a central tube, the orifice 8 into the pumping space II between the upper jet being ñxed at the top of the tube, the tubes 4 and 5. while the lower jet is ñxed about halfway up the The lower jet has its outer member I2 ñxed tube; both jets are supplied with vapor from to the tube 4, While its inner member i3 is fixed the central tube, and the vapor issues from the to the top of a tube I4 attached to the outer jets into the annular space between the central tube 5 at I5. tube and the outer tube constituting the body The mercury in the boiler is separated into of the pump. The efficiency of the pump for a two portions, a. central portion inside the tube 4 given vacuum depends largely on the density' of the vapor issuing from the two jets and on the 15 and an annular portion between the tubes 4 and 5.V The two portions are in communication downward velocity of the molecules in this vapor. lthlrough the holes I9 in the tube 4 below the Now it has been found that, in the described mercury level 2, and the two portions are heated arrangement in which the two jets are supplied together by an electric heater in the space 3. with vapor from the same source, it is generally impracticable to design the two jets so as to pro 20 Mercury evaporated from the annular portion ascends into the space I6 between the tubes Il duce vapor jets with the desired density and and I4 and issues from the lower jets I ï, I3. velocity. There is necessarily a fall in vapor The evaporation from this portion is independent pressure from the bottom to the top of the cen of that from the central portion, and the vapor tral tube to produce a flow up the tube, and the pressure at one of the jets depends on the rate 25 pressure in the tube 4 leading to the upper jet may diiîer from that in the space i8 leading to of ilow through the other jet. The two jets the lower jet, any diiîerence in vapor pressure therefore are interdependent. being compensated by a difference of level of the According to the invention, the two jets are mercury inside and outside the tube 4. supplied with vapor through two non-communi The upper jet, therefore, operates independ cating passages from two non-communicating 30 ently of the lower jet, and the quantity of vapor evaporating surfaces of two communicating issuing from each jet depends only on the di masses of liquid. The upper jet may be sup mensions of the jet and the temperature at plied with vapor through a central tube de which the mercury is maintained. scending below the level of the liquid in the The outer tube 5 is surrounded as is customary boiler and separating `the liquid in the boiler 35 by a water jacket 25, and the outlet 2l of the into a central portion within the tube and an pump leads from the bottom of the space li to annular portion outside the tube, and by the the backing pump. The mercury vapor from lower jet being supplied with vapor from the the two jets is condensed by the cooled wall 5 annular portion of the liquid through a tube be tween the central tube and the pumping space, 40 and falls into the space 22 between the tubes I4 and 5. A mercury seal is formed at this point and holes in the central tube below the level of by the channel 23, and the condensed mercury the liquid giving communication between the two passes through holes 24 in the tube Ië and, over portions. rPhe tube through which vapor is sup flowing the channel 23, returns to the boiler. plied to the lower jet may be connected with the As shown in the drawing, the outer tube 5 pref ~ outer wall of the pumping space through a liquid 45 erably has parallel walls at its upper part sur seal, through which liquid condensed in the rounding the jet l, the annular space between pumping space returns to the annular portion the tube 5 and jet ‘I of width A determining in of the liquid in the boiler. large measure the rate of evacuation of the pump. In the accompanying drawing, which shows in As described and claimed in co-pending appli a single íigure by way of example a form of pump 50 cation No. 596,034 the tube 5 diminishes in di embodying the invention in vertical section, a ameter by the inclusion of a conical wall just mercury boiler I, containing mercury normally below the jet l, which conical wall joins up with up to the level of the dotted line 2, with heater the parallel walls of the lower part of the tube 3, supports the central vapor tube 4 and the outer tube 5 forming the body of the pump, which 55 5, so that the tube 5 diminishes in diameter at rï‘his invention relates to vapor vacuum pumps 2,404,022 a point near jet orifice level so that the length of vapor jet measured along a line B with angle 15 degrees from the general pumping direction, indicated by the line C, does not exceed 2.6 times the width A of the annular space at jet oriñce level. Further as described and claimed in co-pending application No. 596,036 a water jacket 25 may surround, but not touch, the tube 4, for a length just below the jet oriñce 3Y downwards, the jacket having inlet and outlet pipes 26 by which it is continuously supplied with cold water. As fully explained in the aforesaid co-pending application No. 596,036, the eñîciency of the pump is further increased by the employment of this ~15 inner jacket since vapor molecules are thereby prevented from striking the hot tube A and achieving a random velocity which enables such molecules to collide with molecules issuing from the jet 8 and diminish the downward component 20 of their velocity, 't 4 We claim: A vapor vacuum pump comprising a boiler for the vapor, a central tube depending into said boiler and having apertures in its depending part, ' an outer tube Vforming with said central tube an annular space in said boiler, an intermediate tube between said central and outer tubes forming inner and outer annular spaces respectively there between, upper and lower annular jets supplied with vapor from the boiler respectively through the central tube and the inner annular space, and a liquid seal between the lower end of said in termediate tube and said outer tube into which seal falls condensed vapor from said jets and from which the condensed vapor returns to said annular boiler space. PAUL ALEXANDER. CECIL WHILEY.