A Remarkable Vacuum-Pump.
It is a well established fact that no practical means have been devised heretofore to produce a perfect vacuum for commercial purposes. The use of the mercurial air pump has been the only successful method used for exhausting air to the high degree as required in the manufacture of incandescent lamps, laboratory use, etc.; but the excessive slowness of its operation does not allow its general use in the arts. The accompanying illustration shows a belt-driven vacuum-pump which is especially designed for this service and which is capable of producing a perfect vacuum. The photograph of it was taken at the plant of the Westinghou.se Electric Lamp company at Watsessing, N. J., where the pump is installed. It is of the two-stage pattern arranged with two 12-in. diameter vacuum cylinders. 12-in. stroke designed for a speed of 100 revolutions per minute and. under these conditions, will produce a vacuum of within .02 in. of the barometric height as registered by the mercury gage which ts shown in illustration. This pump runs continuously under these conditions and the results obtained are very remarkable. The pump takes suction directly .from a closed receiver which is piped off to the stands containing the incandescent latftps to lie exhausted. The large capacity of the pump, together with its great efficiency, particularly adapts it for this class of service. It works strictly on the dry system, as no water is necessary or permitted to enter the cylinders. It is also adapted for all usages where exceedingly high vacuum is desirable—namely in connection with the evaporative processes of sugar refineries, distilling plants, chemical and dye works glue works, salt works, soap works, the manufacture of prepared foods, medicines, essence, glycerine, etc., preserving processes, the production of high vacuum in central steam condensing systems, and steam turbine works. These vacuumpumps are also built with steam cylinders for direct steam drive, also arranged with extended bases and gearing for electric motor. The vacuum cylinders are thoroughly water-jacketed. The valves are mechanically operated by eccentrics keyed to the main shaft. Experience with work where the highest possible degree of vacuum is required has shown that the correct practice is to handle the air by the means of two air cylinders, that is, in two stages, one cylinder discharging into the other. By reducing the difference in pressure between the opposite sides of the piston, it is possible to take care of the leakage past the piston rings, etc., that may occut in the intake cylinder, which, however slight, seriously affects the capacity and efficiency of the pump on trie Higher ranges at vacuum, atm in mis way maintain a constant vacuum within .02 in. of the barometer. This successful production of a machine, not difficult of management and capable of maintaining an extremely high vacuum, has revolutionised many industrial processes and has opened up new possibilities in the arts heretofore wholly out of reason. Particularly in the case of incandescent electric lamp bulb manufacture, the above type of machine has proven its value. It has simplified former methods and has made easier and cheaper the rapid production of finished bulbs. A more extended application of these pumps is in the production of high vacuum in connection with evaporative processes, etc. With every fractional part of an inch gain in the high ranges of vacuum, the boiling point temperature is reduced in a much greater prooortion. so that, with a given apparatus, the higher the vacuum the greater its capacity, and, incidentally, the greater the improvement in the quality of the prodtict. The indicator cards shown herewith were taken from the two vacuum cylinders. It is interesting to note the difference in the work performed by the intake or suction cylinder and that of the final cylinder. The latter cylinder does by far the majority of the work, while the intake cylinder produces just that fraction of an inch of vacuum which reduces the resultant pressure to practically absolute zero. This machine is manufactured in larger and smaller sizes suitable for various capacities and is designed and patented by the Blake & Knowles Steam Pump Works, 115 Broadway, New York city, where further particulars may be obtained.