A New Rotary Air Compressor
Page 61
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A N ingenious and simply designed air Picompressor and vacuum pump of the rotary type has recently been produced by Northey Rotary Engines, Ltd., 22, Springfield Road, Parkstone, Dorset. The accompanying illustration shows a machine built for operating the vacuum brakes on an oil-engined
chassis. The results of tests show that a high vacuum can be obtained, and that in view of the relatively small size of the machine, the weight of air discharged at high vacua is very considerable.
The rotors are contained within a chamber formed by two intersecting cylindrical bores, they are carried on two shafts, and are geared to revolve in opposite directions. The clearances are arranged so that the rotors do not touch one another, or make contact with the walls of the chamber in which they rotate. The shape of the rotors will be seen in the drawing, and inlet and outlet ports, covered and uncovered by the rotors themselves, are a feature of the design.
As the movements are purely rotary, the machine may be perfectly balanced and the speed is not limited by mechanical consideration. At a speed of 1,840 r.p.m. a vacuum of 25 ins, is obtained in 12 seconds and a maximum of 29.65 ins, vacuum is obtainable.
Due to tee clearance on the moving parts no internal lubrication is required, these clearances are, however. small, so that the leakage losses are low, and the volumetric efficiency is high.
The concern is at present making a number of smaller vacuum pumps, which will weigh in the region of 12 lb., and should be suitable for commercial vehicle requirements.