Abstract
The advent of the self-contained hydraulic press, with its many advantages, has necessitated the development of a compact high-speed pump. For most pressing operations a variable-delivery pump is of little advantage, and such pumps, having rotary valves, are only capable of comparatively low pressures. On the other hand a working pressure of 5,000 lb. per sq. in., with its attendant advantage of compactness, is readily obtainable with pumps having positively seating mushroom type valves. Such a pump is described, which the authors have perfected, and which has a volumetric efficiency of over 97 per cent at 1,500 r.p.m. High volumetric efficiency is essential to obviate noise and vibration at such speeds and to reduce pulsations in the flow to a practically imperceptible amount.
To obtain high volumetric efficiency at high speeds the shape and construction of the suction valves are of paramount importance. Some comparative experimental figures are given for the discharge of valves of various shapes.
Oil is used as the hydraulic medium as it prevents corrosion and ensures that all working parts are copiously lubricated. The pump is immersed in the hydraulic medium and all rotating parts are mounted on ball or roller bearings. The conditions of loading, the effect of deflexion on the journal bearings, and the special design of shaft are fully described. The paper concludes with various illustrations of self-contained hydraulic presses to which this type of pump has been applied.
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