Patent GB-473978-A (GB)
Title: Improvements in or relating to a method and apparatus for producing high vacua by diffusion
IPC: F04F9/00
Filed: 1936-04-23
Abstract: 473,978. High-vacuum ejector apparatus. KODAK, Ltd. April 23, 1936, No. 11580. Convention date, June 21, 1935. [Class 71] In diffusion, jet-pump apparatus for producing a high-vacuum by employing an organic evacuating liquid, volatile impurities or other undesired constituents, which would return to the boiler or high-vacuum side of the pump, are separated and segregated from the evacuating fluid during the operation of the pump. The apparatus shown in Fig. 1 comprises a fire pump A, a fire pump B, with boilers 1, 2 heated by electric means. The boiler B has a jet 3 and a receiver jet 4 connected by a re-entrant chamber 5 with a connection 6 to the space to be evacuated. A water-cooling jacket 7 is provided. The jet 4 is connected at 10 to pump A provided with a jet 12 surrounded by a receiver jet 13, which is provided with re-entrant rings or balls 14, and is connected to a source of suction comprising a mechanical backing-pump. Chambers 5, 11 are connected by pipes 16, 17 to a passage 18 provided with a steel ball 22 which may be moved to either of pockets 19, 20 or a depression 21 by a magnet. Pocket 19 leads to boiler 1, and pocket 20 by pipe 24 to boiler 2 which is connected by a pipe 25 with a small evaporator C provided with a drainage tube 26. A reentrant chamber 27 is connected at 28 with pipe 24 and at 31 with conduit 10. In operation, the ball is moved to pocket 20 and the boilers supplied with butyl-phthalate. Condensate from jet 4 passes through pipe 17 to pump A. Impurity gases from jet 13 are withdrawn by the backing-pump, and impurity alcohols are trapped in chambers 14. The overflow passes into tube 29. Boiler 2 is replenished from boiler 1 through pipe 30. The impurity residue which collects in boiler 2 passes by pipe 25 to the electrically-heated evaporator C. Vapours of useful constituents from the evaporator C pass partly to conduit 10 and are partly condensed in chamber 27 and returned to boiler 2. Impurity residues in the evaporator are periodically drawn off at 26. With the ball in pocket 19, a greatly reduced vacuum is obtained since the impurities are returned to boiler 2. By placing the ball in the three different positions 19, 21, 20 known respectively as worst tandem, normal tandem, and best tandem, the workings of the apparatus under different conditions can be. compared. In a modification, the chamber 5 is connected directly to the pump 1 and the evaporator is dispensed with. A construction is described wherein the pump A is a direct jet pump, and pump B is of the inverted jet type. The pump B is connected to an evaporator. The impurity alcohols are separated by fractionating-rings. A singlestage pump of the " Langmuir " type is shown in Fig. 4. A tube 50 is led from the boiler A to a separating fractioning column 52 with re-entrant bulbs 53. The column 52 is connected to a backing-pump. A chamber 55 is connected by a pipe 56 to a space to be evacuated. A bulb 56<1> connected to the cooled tube 57 is connected to the column 52 and by a pipe 60 with a vapour trap 61 to the tube 50. A double inverted jet pump is described. The boiler, condensing tube, and a conduit leading to a fractionating-column are lagged. The condensing-tube is cooled by a blast of cold air. The bottom of the jet tube is flared to cause the condensate, which returns to the boiler along its exterior, to contact the rising hot vapours. A multi-stage, cascade pump for a mixed organic fluid is shown in Fig. 6. A metal box 79 is provided with a steel flange 80, a conduit 95 leading to the space to be evacuated, and a water-cooled, sheet-glass, upper surface 81. The box is provided with bent partitions 86 .. 93 spaced from the surface 81. The partitions form jets g ... a which increase in narrowness. The high-pressure end of the pump is provided with a conduit 96 leading to a backing-pump. The chamber is heated by a resistance coil 99 tapped in three places to facilitate regulation. The operation is described with a working-fluid comprising normal amyl phthalate and phenyl and ethyl phthalate. In a modification, a cooling-jacket is arranged around the highvacuum conduit 95. U.S.A. Specifications 1,320,874, 1,367,865, and 1,393,550 are referred to.